Geology Midterm Exam 2

Tin production

Top producers: China, Indonesia, Myanmar, Bolivia/Brazil/Peru Largest reserves: China, Indonesia, Brazil

Examples of tourmaline gemstones

Watermelon tourmaline Indicolite Rubellite Paraiba tourmaline Canary tourmaline Verdelite

Extraction - mining methods

We found an ore body and we determined it is economic to mine. Now how do we get the ore out of the ground? 1. Surface - Open pit - Strip 2. Underground (1 and 2 most common methods) 3. Hydraulic --> used for very specific ore deposits

Skarns

contact metamorphic, calc-silicate rock that forms when carbonate rocks are subjected to metamorphism and metasomatism - Rich in Ca-bearing silicate minerals

Bushveld Complex

most important and famous LMI (produces majority of world's PGEs; formed purely magmatically) Platreef: up to 65 ft thick but can only be traced for 19 mi on surface Merensky and UG2: <3 ft thick but nearly 185 miles surface trace In some places, mined down to 1.25 miles

Gold rushes

new discovery of gold attracts large numbers of people to the area to seek their fortune. this can create "boom towns" like Dahlonega, Georgia

subduction zones

silica-rich Celtic rocks produced the volcanic arc --> Hydrothermal and magmatic ore deposits may form

hydrothermal vents

spots on the ocean floor where hot gases and minerals escape from earth's interior into the water underwater hot spring - seawater percolates into oceanic crust and is heated up by magma at divergent boundaries. the hydrothermal water is re-emitted; forms "chimneys" when minerals crystallize

Hydrothermal ore deposit fluids - surface water

surface water (rain, runoff) percolates through the bedrock from the surface CONTINENTAL crust

Metasomatism

the process by which a rock's overall chemical composition changes during metamorphism because of reactions with hot water that bring in or remove elements

magmatic ore deposits

a magma chamber has the potential to crystallize many types of minerals as it cools - form via fractional crystallization and gravity settling (occur @ same time)

placer deposit

an accumulation of valuable minerals formed by gravity separation during sedimentary processes can increase the concentration of ore mineral; streams deposit sediments along their banks in sand or gravel bars and in alluvial fan or delta deposits minerals must have high density and low reactivity to form placer deposits

Quarry

an open pit mine specifically for excavating building stone (NOT ore - just building materials)

magmatic ore deposits - gravity settling

early formed minerals (highest crystallization temperature) sink to the bottom of the magma chamber one of the layers may be sulfide minerals (now we've formed an ore deposit)

pegmatites

elements that like to stay in melt (incompatible elements) end up crystalizing from the residual melt into pegmatite (e.g. Lithium) often form gems which may be considered ores (because of their human value) though they aren't metals

Hydrothermal ore deposit fluids - seawater

fluid may originate from seawater that percolates through oceanic crust - cold water sinks into crust - water heats up (magma) - hot water rises and reacts with rock to precipitate ore-bearing minerals OCEANIC crust

volcanogenic massive sulfides (VMS)

form at hydrothermal vents on the ocean floor @ divergent boundaries 2,000-4,000 meters below surface VMS deposits are formed (and are currently forming) at divergent boundaries on the ocean floor We mine VMS deposits in Canada, Spain, Russia, Japan

US Consumpton of gold for jewelry

has seen a 5% increase recently due to improving economic conditions

Ore mineral in placer deposit must have ____density and be _____

high density, low reactivity

mechanical weathering

weathering processes break down pre-existing rocks, forming loose grains (sediments) big rocks become little rocks; could contain an ore mineral ex: water freezing and thawing between cracks

Carat - diamond

weight (1 carat = 0.2 grams) - 1 carat most popular size - but you can get better deal getting even a 0.95 carat, because at 1 carat the price starts skyrocketing

xenocryst

A crystal (such as diamond) foreign to the igneous rock in which it occurs (formed elsewhere and transported by the magma)

What type of copper ore deposit was likely mined at the beginning of the Copper Age? A deposit that contained both copper and a by-product metal. A deposit in which copper was a native metal. A deposit in which copper was hosted by the mineral chalcopyrite (CuFeS2). A deposit that was located several miles below the surface. A deposit that contained a low grade of copper.

A deposit in which copper was a native metal.

Examples of beryl gemstones

Goshenite Heliodor Morganite Aquamarine

Economic minerals/commodities found in clastic sedimentary deposits

Gravel, quartz, rutile, chromite, rare earth elements, tin, diamond, mercury, copper, silver, gold, platinum

What type of climate would you expect chemical sedimentary ore formation?

High temperature environment with low precipitation and some body of water

Hydraulic mining

High-pressure jets of water Used for placer mining Water used to wash sediments into sluice boxes filtering out some sediments (that you don't want) (mobilize loose rock and put into sluice box, shake it to get gold out ) Very destructive - Devastated river habitats - Destroyed many salmon fisheries - Many rivers will simply not be the same for 100s and 1000s of years - Put tremendous amounts of silt into rivers, clogging bays that they flowed into - E.g., San Francisco Bay during California gold rush

Considering color only, which of the following would be a cheaper substitute for a blue diamond? Rubellite Indicolite Watermelon tourmaline Paraíba Canary tourmaline

Indicolite

Differences in attitude toward bison

Indigenous peoples killed 1-2 bison at a time and used entire animal for food, clothing, etc. White asses would get on trains and kill entire herds for sport, leaving their dead bodies and taking advantage of bison instinct to stay around dead bison

energy vs grain size (placer deposits)

larger and denser sediments require more wind, stream or wave energy to stay afloat

Xenolith

Country rock fragment in magma

4 categories of ore-forming processes

Magmatic, hydrothermal, sedimentary and surficial

Ore

rock containing concentrated valuable minerals

transform boundaries

plates slide past each other; no magmatic or hydrothermal ore deposits

Gold

"Geolo" means yellow Chemical symbol Au (Latin "aurum" means "shining dawn")

Tungsten - Uses

(Historical) tungsten filaments - Not efficient, produce lots of heat instead of light Tungsten carbide - Extremely hard, can be heated to high temperatures without melting - E.g., drill bits, jewelry Wiring, electrodes, and contacts Heavy metal alloys - E.g., aerospace, turbine blades, ballistic missiles and other armaments

Properties of Copper

- Can occur naturally as pure copper (native element) but MORE COMMON as sulfide and carbonate minerals (ex: chalcopyrite, bornite, malachite) - Similar properties to gold and silver (malleable, ductile, conductivity) - Valuable, but not a precious metal like gold and silver b/c not rare - NOT a noble metal (Tarnishes)

Properties of gold

- Commonly occurs naturally as pure gold - Can combine with other elements to form rare gold-bearing minerals - As a metal it can be alloyed with other metals to vary its physical properties - Extremely malleable

Chemical weathering (surficial processes)

- Concentrates insoluble elements by dissolving out more soluble components - Requires liquid water (high rainfall/humidity --> more chemical weathering) - Different minerals chemically weather and dissolve differently (quartz is resistant to chemical weathering; potassium feldspar crystals break down and form clay minerals due to chemical weathering) - Can only act on the surface of a rock or mineral or where a crack allows air and water into the mineral/rock

History of Silver - Old World

- Decorative and functional purposes - Less rare than gold --> currency - Oldest silver mines in Turkey and Armenia - Greece took over production in 1200 BC and dominated for 1,000 years - New mines later found across Europe

Millesimal Fineness

- Describes the purity of a metal - Used for all metals that are not gold - Out of parts per thousand (1,000 is pure) The purest silver ever produced --> 999.99 (Bolivia) Sterling silver --> 925 (alloy with copper; 92.5% silver)

Karat

- Describes the purity of gold 24 Karat (24 K) = 100% gold Jewelry is typically <24K because pure gold is too soft and expensive Karats lower than 24K are alloyed with one or more other metal(s) 12K- Wal-Mart 18K- moving into nicer jewelry

Cyprus-Type massive sulfides

- Example of a specific type of massive sulfide mineralization - Massive sulfide within an ophiolite complex - Basalt is extruded at divergent boundaries - Also formed on oceanic crust (obducted onto continent)

Uses of Copper

- Highest electrical conductivity of all non-precious metals (wiring and other electronic applications) - Most of copper demand in US for building construction (corrosion-resistant after patina develops, durable, waterproof) - Sheathing on ship hulls protects from barnacles and improves speed - alloys well w/ metals like zinc, tin and nickel (changes properties; for example brass is more malleable and has acoustic properties --> instruments)

How do VMS deposits form?

- Metals are sourced from both magma and oceanic crust - Massive sulfides are deposited due to rapid cooling of hydrothermal fluid when it reaches seafloor - Form metal zones with higher solubility metals depositing further from vent and lower solubility metals (like Cu and Ag) depositing close to vent

History of Copper

- Over 10,000 year history - First metal known to man (more common than gold/silver) - Used for nearly five millennia before other metals discovered - Oldest metal tool in Middle East - Smelting simple copper oxides as early as 5000 BC (before other metals were even discovered, people were able to turn copper into liquid and cast tools) - Alloyed with copper by 3000 BC (commonly alloyed with arsenic and tin)

Platinum group minerals

- Rare minerals - Native elements, native metal alloys or within non-metal materials (Pt-Fe, Pt-As and sulfide minerals) - Commonly a mixture of multiple PGEs - Enrichment of one PGE over another depends on geological conditions of formation

History of Silver - New World

- Silver discovered in the Americas by the Spanish in late 1490s - Mines established in Mexico, Peru and Bolivia dominated production - Silver traded around the world - Some consider this to be the beginning of a global economy

PGE deposits

- Total concentration of PGEs does not need to be very high due to high value and good recovery rates - Minor acts of PGEs can be found in Au and Cu deposits (as secondary commodities)

Sulfides

- mineral class with S2 anionic group - commonly contain metal cation - silver is more commonly found in sulfide minerals than as a native element - massive sulfide - the rock is all/mostly heavy sulfide minerals

Epithermal Gold deposits

<1 mile depth Either quartz veins with other precious metals or disseminated and low-grade with other precious metals Magmatic fluids mix with surface fluids Active volcanic regions on continental crust Found in younger crust because older have already been weathered and eroded away Make lots of other metals in addition to gold

PGE deposit types

1. Layered Mafic Intrusion (LMI) - South Africa (Bushveld Complex), Montana, Zimbabwe 2. Meteorite impact (unique) - Canada

Two main types of gold deposits

1. Lode --> Primary; metal actually formed there 2. Placer --> Secondary; metal carried to this area, did not form there

types of lode gold deposits

1. Orogenic (deepest) 2. Intrusion-related 3. Epithermal (closest to surface) - Can be roughly distinguished based on depth in continental crust - All primary deposits (form gold themselves) - Form at oceanic-continental convergent boundaries (subduction zones)

Types of copper deposits

1. Porphyry (Also one of the intrusion-related gold deposits) VMS also important for copper, though porphyry are dominant

Underground mining methods

1. Room and pillar 2. Longwall mining (these two are used for layered deposits, like coal) 3. Tunneling to follow non-layered ore bodies (e.g. veins) Method used to mine depends upon type of deposit - shape, size, grade Drilling and blasting is used in most mines - then removal with automatic diggers onto rail cars or elevators to the surface Coal mines often use continuous mining machines

Types of Silver deposits

1. Veins 2. Massive sulfide deposits

Tin and tungsten deposits

1. Veins 2. Skarns 3. Porphyries 4. Placer (tin only)

Intrusion-Related Gold Deposits

1.25-4.25 miles depth Contain many different kinds of deposits Fluids sourced from felsic magma systems (closer to surface than orogenic)

early blast furnace

1340 AD = major breakthrough Large amounts of iron could be produced (smelted to make cast iron) Combustion air forced into furnace above atmospheric pressure Fuel and ore continuously supplied to top of furnace Requires charcoal energy for fuel

Bison distribution

1500s = 25-30 million Late 1880s = < 100 territory seriously shrunk

Population and resource use

1770-1900: population doubled, mineral production grew 10x 1900-1970: population increased by 2.3x, mineral production grew 12x (so similar rate) 1970-2000: population doubled again and mineral production tripled! Population increasing, but also, resource use per capita is dramatically increasing.

Tin Can

1795: Napoleon Bonaparte needed to preserve food for military use 1810: Nicolas Appert, a French chef, invented canning Peter Durand patented tin-plated steel to can food - Tin is corrosion resistant - Too expensive to make the whole can out of tin 1813: the first canned goods produced for the Royal Navy Coors invented the first aluminum can in the 1950s

Hemp

1930s: new machinery that separated the fiber from the rest of the hemp plant was available and affordable Harvest and production was easier and more cost effective 1937: US introduced prohibitive tax laws on hemp and later banned it entirely Influenced by synthetic textile companies 1938: DuPont patented a "plastic fiber" called Nylon

History of Gold - Middle Ages

6th century gold mining by the Byzantine Empire in Central Europe and France Venice introduced the widely popular gold Ducat

Platinum group mineral*

A material that has all the properties of a mineral and contains one or more platinum group elements - must be NATURALLY OCCURRING - can contain other elements that are not PGEs - could also be an alloy

Lode gold deposit

A mineral deposit whose principal commodity is gold and that has typically been deposited by hydrothermal processes

If silver has relatively low solubility where in a VMS deposit would you expect to find it and why? A. Closer to the vent/pipe because the temperature is higher. B. Closer to the vent/pipe because the temperature is lower. C. Closer to the edge because the temperature is higher. D. Closer to the edge because the temperature lower. E. In the discharged hydrothermal fluid - it would stay in solution.

A. Closer to the vent/pipe because the temperature is higher

What type of ore-forming process formed the Bushveld Complex? A. Magmatic B. Hydrothermal C. Sedimentary D. Surficial E. Both A and B

A. magmatic

Surface mining

Accounts for two thirds of the world's mineral production Especially the production of sand and gravel, crushed stone, and phosphates, coal, copper, iron, and aluminum Generally lower grade ore This includes open pit mining and strip mining ex: Bingham Canyon Mine, Utah Ore is dug out, processed - Non-ore rock that is dug up is put in waste rock pile - ~2-3 tons of waste rock per ton of ore Waste from processed ore goes into tailings pile Significant land disturbance

Platinum group metal*

All PGEs are metals, but this term generally refers to alloys of PGEs (naturally occurring or man-made) Must be 100% ONE OR MORE PGEs

What type of ore deposit is shown in the image below? Skarn Porphyry Epithermal Vein All of the above

All of the above

Which of the following properties does diamond possess that make it a gemstone? Beauty Durability Rarity All of the above Diamond is not a gemstone

All of the above

Pewter

Alloy with 85-99% tin and 5-10% antimony (Sb) - Other metals include copper, bismuth, and silver - Increase hardness, lower melting point by alloying - Decorative items and plates, cups, bowls Historically contained lead - E.g., lead leaching from pewter tankards caused heavy metal poisoning and gout - Somerset, UK: cider-drinking, acidity leached lead more quickly

Tin alloys

Alloyed with copper to make bronze since 3000 BC Arsenic + copper first used to make bronze; Arsenic associated with copper ore (Health risks quickly realized) High demand for tin to make bronze Tin oxide used because easier to separate out the metal Tin oxide minerals concentrate in placer deposits Easy to mine Pure metal not used until ~600 BC (only bronze alloy at first)

porphyritic texture

An igneous rock texture in which large mineral grains (phenocryst, slowly cool underground) are scattered on a background of much smaller mineral grains (groundmass, cool quickly underground or on surface).

At which tectonic margin type would you be most likely to find a porphyry deposit?

An oceanic-continental margin

Change in diamond market

Competition from other diamond producers: 1950s Soviet Union 1980s Australia 1990s Canada Consumers started to demand conflict-free diamonds

Myth of scientific supremacy

Arguably replaced the myth of superabundance once it was exposed in the 20th century (The Quiet Crisis) Myth of scientific supremacy: the belief that science will find a solution to any problem, including environmental crises. i.e., the problems of technology will be solved by more technology

Diamond history - 13th to 17th centuries

Around the 13th Century, diamonds can be documented as gemstones in Europe. - Adorned royal jewelry; symbols of power Diamonds began to be faceted - Started in either Venice or Antwerp Wearing diamonds reserved for royalty until the 17th Century - Following this, only the wealthy upper-upper class could afford them Jewelry design shifted: diamonds (and other gemstones) became the center of attention instead of just part of an art piece - Diamond cutting became important

Largest gold reserves

Australia, South Africa, Russia

What is the dominant type of ore-forming process that forms porphyry deposits? A. Magmatic B. Hydrothermal C. Sedimentary D. Surficial

B. Hydrothermal

How are veins formed? A. Magma migrates into fractures and faults within country rock. B. Hydrothermal fluids migrate out of a magma body into fractures and faults within country rock. C. Gases migrate out of a magma body into fractures and faults within country rock. D. Surface water migrates down through country rock via fractures and faults. E. Pre-existing minerals along fractures and faults are metamorphosed into new minerals.

B. Hydrothermal fluids migrate out of a magma body into fractures and faults within country rock.

Which statement best describes a naturally occurring Pt-Au (platinum-gold) alloy? A. It is a platinum group element, a platinum group metal, and a platinum group mineral. B. It is a platinum group mineral, and it contains both a platinum group element and a platinum group metal. C. It is only a platinum group metal. D. It is only a platinum group mineral. E. It is a platinum group metal, it contains a platinum group element, and it is not a platinum group mineral.

B. It is a platinum group mineral, and it contains both a platinum group element and a platinum group metal. It is not a platinum group metal on its own because all the metals in the alloy are not PGEs, but it contains a PG metal; it is not a PGE by itself because it contains more than one PGE

If hydrothermal processes, felsic magmatism, and metamorphic conditions are required to form orogenic gold deposits, in which type of tectonic setting would they be formed? A. Continental-continental convergent boundary B. Oceanic-continental convergent boundary C. Oceanic-oceanic convergent boundary D. Transform boundary E. Divergent boundary

B. Oceanic-continental convergent boundary

Which of the following statements about orogenic and placer gold deposits is true? A. Orogenic gold deposits are always higher grade than placer. B. Orogenic gold deposits are a type of primary deposit while placer are secondary. C. Orogenic gold deposits are easier to mine than placer. D. Orogenic gold deposits are no longer forming on Earth while placer are still forming. E. Orogenic gold deposits are formed on oceanic crust while placer are formed on continental crust.

B. Orogenic gold deposits are a primary deposit while placer are secondary (Placer - not formed there, have been eroded)

Why are copper porphyry deposits mined using open pits? Because they tend to be low grade deposits Because the copper tends to be disseminated within the rock Because they can be found close to the surface Because they tend to contain a high tonnage of ore Because of all of the reasons above

Because of all of the reasons above

Orogenic gold deposit

Below 3 miles deep (3-6 miles deep) Low-grade, regional metamorphism (squishing pressure) Areas of active faulting (cracked rock being moved on either side) Subduction causing melting of rocks in lower crust Granitic melts migrate upwards, contributing additional heat and (gold-bearing) fluids to areas undergoing faulting Vein - rock fills fault fracture

Beryl (Be3Al2Si6O18) is commonly found in pegmatites. Pegmatites are enriched in incompatible elements compared to other igneous rocks. What is the incompatible element in beryl? Beryllium (Be) Aluminum (Al) Silicon (Si) Oxygen (O)

Beryllium (Be)

Iron Age

Bronze Age ended ~800 BC Iron Age: iron/steel tools and weapons produced that are superior to bronze equivalents Iron began to be worked around 1300 BC First iron worked came from meteorites Dominantly iron-nickel alloy Working iron requires more energy than working copper The first iron could not be smelted easily, like copper, just heated enough to be reworked into useful items. Since iron has a higher melting temperature than copper, it must be smelted in a very hot fire and this required charcoal

Bronze Age

Bronze age: humans started to work with metal (making alloys) Bronze is copper alloyed with tin (and sometimes other additional metals e.g., silver, lead, or arsenic) A problem: In parts of the world where copper ores were plentiful, tin was rare. two metals not easily accessible together The only known large deposits of tin in the ancient world were in western Great Britain Establishment of tin trade routes led to the Bronze Age First large-scale "international" trade

Copper alloys

Bronze: Copper-Tin alloy Brass: Copper-Zinc alloy

In what type of geologic setting would you expect to form this porphyritic rock? A. Divergent boundary B. Oceanic-oceanic convergent boundary C. Oceanic-continental convergent boundary D. Continental-continental convergent boundary E. Transform boundary

C. Oceanic-continental convergent boundary

Which of the following is the primary reason that a jeweler would use platinum instead of gold? A. Platinum can be alloyed more easily than gold. B. Platinum has a more desirable color than gold. C. Platinum is more durable than gold. D. Platinum is less expensive than gold. E. Platinum has higher electrical conductivity than gold.

C. Platinum is more durable than gold

Which of the following statements about silver and gold is false? A. Silver is less valued by humans than gold. B. Silver is more reactive than gold. C. Silver is never alloyed with other metals like gold is. D. Silver and gold both have industrial applications. E. Silver is less dense than gold.

C. Silver is never alloyed with other metals like gold is.

Review: What type of ore deposit is forming at the location in the image below? A. Orogenic gold B. Placer C. Volcanogenic massive sulfide D. Porphyry E. Layered mafic intrusion

C. Volcanogenic massive sulfide

Carbon Steel revolution

Carbon steel is stronger and easier to work, plus its more flexible Flexibility allowed it to be used in for construction

Why can't we use grade to value diamond deposits?

Care about their cut, color, clarity rather than just their presence

Coke

Cast iron did not meet the needs of technology Carbon content too high, metal too brittle To produce higher quality iron alloys, a higher energy source was needed Coke: high-carbon fuel produced when coal is heated in the absence of air (drives off volatiles) Burns hotter than coal ~1740: creation of carbon steel (<1% carbon) by blowing air through molten iron Harder and more workable product Needed to make carbon steel

What new energy source was required to smelt iron and make cast iron? Coal Wood Oil Wind Charcoal

Charcoal

Graphite

Chemical formula = C Pencil "lead" Diamond and graphite have very different crystal structures that reflect the different ways there are formed.

Diamonds

Chemical formula: C Grow naturally as octahedra Extremely high hardness High dispersion (splits light into different spectral colors) High thermal conductivity

Silver

Chemical symbol: Ag (from "argentum" in Latin)

Largest copper reserves

Chile, Australia, Peru

Top copper producers

Chile, Peru, China, Democratic Republic of Congo/USA are tied There has been a slight increase in production (less supply disruptions as temporarily closed mines have reopened) and slight increase in consumption

Top producers of gold

China, Australia, Russia, US, Canada There has been a relative decrease in production of china due to increased environmental regulations in recent years

Gold alloys

Closer to edge - more of that color Can be mixed with silver to form white gold or mixed with copper to form rose gold; each triangle tip is 100% that metal

What fuel resource was necessary for the production of carbon steel? Coal Wood Oil Coke Charcoal

Coke

4 C's (diamonds)

Color, Clarity, Cut, Carat

Why the shift toward non-renewable?

Combination of new products and markets, and material replacements in established markets Synthetic fibers have replaced natural fibers Plastics have replaced wood Synthetic oils have replaced natural oils Replacements have more desirable properties or cost advantages The US was self sufficient in mineral production in 1875, but now relies heavily on other countries. With 5% of the world's population, the US uses 30% of the world's mineral resources.

History of Silver - Rise of North America

Comstock Lode discovered in Nevada in mid 1800s - Silver rush - Once surface ore was extracted, mining went underground - Cave-in and flooding problems led to mining innovations More sophisticated mining techniques = greater extraction rates - Deposits in Colorado, Utah, Idaho, and British Columbia

Making charcoal

Cooking wood in a low oxygen environment Process burns off volatiles such as water, methane, hydrogen, and tar makes more concentrated fuel source

Pegmatites have extremely large crystals (up to meters long). How do they form?

Cool SUPER fast! (not what you'd expect) Pegmatite-forming magmas are enriched in incompatible elements that act as fluxes

The 5th C (diamonds)

Country of origin - *Not formally recognized by the GIA, but increasingly demanded by consumers.

Pegmatite zoning

Crystallize from the outside to inside Increasing degree of fractional crystallization as we move to inside (inside has more incompatible elements) Pegmatites can be distinctly zoned Different minerals are more prominent in different zones Best zones to find gemstones (intermediate-core)

What is the composition of this porphyritic rock and what are the main minerals that it contains? A. Mafic; amphibole and pyroxene B. Mafic; quartz and felspar C. Felsic; amphibole and pyroxene D. Felsic; quartz and feldspar

D. Felsic; quartz and feldspar

What type of gold deposit is most likely mined during a gold rush? A. Orogenic B. Intrusion-related C. Epithermal D. Placer

D. Placer

Diamond history - India

Diamond appreciation and mining began in India The Sanskrit word for diamond, "vajra", first appeared in 4th C BC Perfect shape (octahedron) most valued, but fire and brilliance also recognized as valuable.

Kimberley Process (KP)

Diamond industry program designed to ensure that diamonds crossing international borders are legitimate and do not fund civil conflict or terrorism Eliminate blood/conflict diamonds Stable countries that produce conflict-free diamonds are endorsed - Production includes mining, cutting, and/or polishing Diamonds are tracked and can only be sold to countries that conflict-free All countries have strict regulations for exporting and importing diamonds Facilitates the trade of legitimate diamonds - 81 countries - 99.8% of global diamond production Some have more weight than others - E.g., US imports huge quantities of diamonds - being part of KP is big deal - E.g., Kazakhstan is part of KP but does not import or export diamonds, not big effect

Diamond growth

Diamonds are only stable at extremely high pressures, deep within the Earth (at least 87 miles) - Rocks at these depths are ~2700 °F (Too hot for diamonds to grow; Diamonds form at ~1750-2550 °F) There needs to be a "cool" region that still exists at great depth These "cool" regions exist at the base of Archean cratons.

Issues with Kimberley Process

Diamonds are relatively easy to smuggle Some countries in the KP have imperfect track records of compliance (Cote d'Ivoire, Zimbabwe, Venezuela) - E.g., Diamonds from Zimbabwe mined from the military-controlled Marange Region are not considered conflict diamonds by the KP KP is relatively good at monitoring large-scale production (e.g., kimberlite mines), but can have difficulty with artisanal-scale operations (e.g., placer) The KP cannot be the only solution to stopping the trade of conflict diamonds.

How do diamonds reach the surface?

Diamonds form under ~87 miles or more of cold cratonic rock. To reach surface, require kimberlite volcanoes

VMS Metal Zones

Different metals precipitate out of solution at different temps If a metal can stay in solution at lower temps, it has higher solubility Silver has relatively low solubility --> find it closest to vent where temperature is high

Mineral solubility

Different minerals dissolve at different rates (dissolution is a type of chemical weathering) Quartz and clay have low solubilities Calcite is more soluble Salt (halite) is very soluble

PGEs - History 16th-19th century

Discovered in Colombia in 16th century by Spanish Interpreted as "unripe gold" Nuisance to placer gold miners as it was unmeltable Not recognized as a distinct element w/ unique properties until mid 1700s Used in jewelry but not as much as gold and silver (much more rare, more durable, difficult to work with, and Louis XV of France declared the metal was "fit only for a king")

Hydrothermal ore deposits - disseminated vs vein ores

Dissiminated: pieces that contain metal are scattered all over (have to mine much more non-ore rock) Veins: concentrated together along a lined structure (easier to mine)

sedimentary ore deposit formation

Dissolved ions in water derived from chemical weathering are left behind as water evaporates. Concentration of ions in remaining water increases as evaporation continues. Saturation is reached & minerals crystallize to form chemical sedimentary rocks high evaporation rates needed --> climate is important

If 24-karat gold is pure, which of the following is correct? A. 18-karat gold = 75% gold, 25% silver B. 18-karat gold = 18% gold, 82% other metal C. 18-karat gold = 25% gold, 75% other metal D. 18-karat gold = 75% gold, 25% other metal E. Both A and D

E. Both A and D

What is the main distinguishing factor between the different types of lode gold deposits? A. The type of rock the gold is hosted in. B. The type of process that formed the ore. C. The grade of the ore deposit. D. The depth they are currently found at. E. The depth they were formed at.

E. The depth they were formed at.

How do biological sedimentary rocks form? A. They form when a rock made of biological material is subjected to high heat and pressure. B. They form when clastic sediments are lithified into a rock. C. They form when weathering and erosion break-down pre-existing rocks. D. They form when minerals are precipitated out of a saturated solution. E. They form when plants and animals die and accumulate on the ground or seafloor.

E. They form when plants and animals die and accumulate on the ground or seafloor.

Platinum group elements tend to have ____ melting points and ____ density. A. low, low B. low, high C. moderate, moderate D. high, low E. high, high

E. high, high

The Bushveld Complex in South Africa is the most important PGE deposit in the word because: A- It is located in the only country in the world that has a demand for PGEs. B- It is the only layered mafic intrusion in the world. C- It is the only PGE deposit that is located at the surface of the Earth. D- It is located in the only country in the world that allows PGEs to be mined. E- It produces the majority of the world's PGEs.

E. it produces the majority of the world's PGEs

History of Gold - The ancient world

Egypt - associated w/ sun; hieroglyphs described gold and skins of gods were considered golden; standard medium of exchange for international trade; beat gold into leaf (flat layer) and alloyed with other metals to improve hardness/vary color Greece - thought it was made from dense combination of water and sunlight; started mining in 550BC; mined into Asia Minor and Egypt and practiced alchemy (turning 'base metals into gold') Rome - developed new technology to mine gold (divert streams; pioneers of roasting to separate gold from waste rock); aureus gold coin - Roasting is awful for environment

PGEs - Early History

Essentially unknown until 16th century Small box in Egyptian casket of Thebes constructed from gold, silver and a PGE alloy

Diamond Industrial Applications

Extremely hard → the hardest natural substance Used as a cutting tool Excellent thermal conductivity All the diamonds that humans don't value for their looks ~80% of all diamonds mined

Formation of skarns

Felsic magma emplaced in bedrock containing carbonate rocks cools and releases hot, metal-rich fluids that move through surrounding country rock (metals are incompatible w/ magma and concentrate in hydrothermal fluids)

History of Gold - Modern

First US gold rush in North Carolina - North Carolina supplied all domestic gold coined for currency for 25 years Gold flakes found near Sacramento, California when building sawmill (California Gold Rush) - Remains one of the most prized metals to this day (Olympic medals, Nobel prizes, Academy awards) - Technological tool

Archean cratons

Found in the middle of many continents Very, very old (> 2.5 billion years) and very thick Push a keel down into the upper mantle At the base of the keel is an environment suitable for diamond growth (High pressure and "Cool" temperature) This environment is the "diamond window". Outside of it, pure carbon is graphite The non-cratonic lithosphere does not reach high enough pressure for diamond formation Diamonds won't form in the asthenosphere (extreme pressure, but too hot)

Pegmatite crystallization

Fractional crystallization is very important for pegmatite formation Some minerals crystallize before others When they crystallize, whatever elements they are composed of are removed from the melt (E.g., Quartz crystallizes, SiO2 is removed) Compatible elements (those that like to go into solids) will become part of these minerals while incompatible elements stay in the melt Result: the residual melt is enriched in incompatible elements Incompatible elements include "rare elements" (e.g., Be, Li, Nb, Ta) and also volatile elements (B, P, F, H2O) Pegmatites form from the last remaining part of a granitic melt, already enriched in incompatible elements This melt has already undergone fractional crystallization This residual melt crystallizes, again undergoing fractional crystallization - Incompatible elements become super concentrated --> Weird minerals

Gemstone

Gemstone (or "gem"): Any mineral that is highly valued for its beauty, durability, and rarity. Doesn't have to be a mineral (could be organic or synthetic) Could be a rock Some of these qualities are more important for some gemstones than others (E.g., aquamarine isn't that rare, but it is beautiful and durable)

History of Silver - The Modern Era

Highest grade silver deposits are depleted We are now exploiting resources that had once been too low grade Silver is mainly mined as a by-product from poly-metallic deposits (Pb-Zn and Cu-Au mines; mined where other metals are the primary metal desired)

Silver Veins

Historical source of silver (didn't require sophisticated mining methods to produce pure silver) Native silver or silver-lead-zinc Single veins can be ore bodies if wide enough (several feet) Thin veins are components of larger ore deposits

Diamond sources

Historically sources were extremely rare and alluvial (river gravels) placer deposits Golconda Region of India 18th Century: diamonds discovered in Brazil, but only produced a max of 50,000 carats over several years 1867: diamondiferous kimberlite pipes discovered in South Africa - Diamonds became more common for royalty and the upper class - With more mining, middle class also able to obtain diamonds

Tin/Tungsten Veins

Hydrothermal fluids from felsic magma deposit tin in faults and fractures in surrounding rocks Veins found above magma body (but still under surface)

Clarity - diamond

Ideally no inclusions (clear/flawless) but this is very rare - Scaled from internally flawless to inclusions Flaws include mineral inclusions, fluid-filled inclusions, clouds, feathers, scratches and abrasions - Carat often sacrificed to improve clarity

Color - diamond

Ideally should be colorless but almost all have a yellow undertone - GIA color scale: D-F colorless, G-J near colorless, K-M faint, N-R very light, S-Z light - D-F/I will appear colorless to the untrained eye - Beyond Z, termed "fancy"

Why does the magma in diamond-bearing kimberlite volcanoes have to ascend to the surface extremely quickly? If the process is not rapid, the magma will not have enough energy to pick up and move the diamonds. If the process is not rapid, the diamonds will start to convert back to graphite. If the process is not rapid, the magma will not have enough energy to make it through the thick craton. If the process is not rapid, the diamonds will all break up into smaller pieces along the way to the surface. It doesn't have to ascend quickly, that's just what happens.

If the process is not rapid, the diamonds will start to convert back to graphite.

Pegmatites

Igneous rock Intrusive Generally felsic (Minerals are mainly quartz and feldspars) Known for having large crystals, unique textures, and rare minerals

Room and pillar method

Implication: you have to leave some of the ore to hold up the cavern to avoid roof collapse After mining ore, "rob pillars" - This was done in coal mines when the high grade coal was exhausted - Typically when the mine was near the end of its life - Result: mine collapse, miner death - Regulations in the US now prevent this from happening

Diamond treatments

Improve or change color: - Diminish or eliminate the yellow undertone - Create fancy colors Improve clarity: - Fill fractures with glass - Bleach or dissolve out inclusions - Increase the value Diamond merchants are supposed to disclose any treatments applied - Treating an already treated stone can damage it

US consumption of materials

In 1900 almost half of the materials consumed were from renewable resources By 1995 consumption of renewable resources had declined dramatically, to only 8% of total consumption It is believed that the amount of minerals consumed by the US, since the end of the second world war alone, is more than the total volume of minerals consumed since man started using minerals.

Underground mining

Includes use of tunnels and/or vertical shafts under the ground or into a mountain. Usually smaller operations (i.e., a few 100,000 to million tons over the lifetime of a mine). With small tonnage, needs high-grade ore Less land disturbance - Impact on land can't be seen Less waste rock - Waste rock can be moved to the surface or used to fill in mine areas no longer in use Used to extract a mineral resource that is too deep to allow for economic surface extraction (High grade ore) Potential issues: Ventilation - many smaller shafts needed for ventilation Flooding can be a problem Temperature - gets hotter with depth Mine collapse

Which of the following was not an effect of the Industrial Revolution? Increased environmental regulations Greater environmental degradation Diversified metal use Increased resource use Poorer working conditions

Increased environmental regulations

Intrusive vs. Extrusive Igneous Rocks

Intrusive (plutonic) - magma cools very slowly beneath the surface (large crystals; visible to the naked eye) Extrusive - lava cools quickly on surface; crystals are too small to see

History of Gold - Early modern

Isaac Newton fixed price of gold in Britain. Gold discovered in Brazil (1700) and became largest gold producer by 1720 Gold discovered in US in 1799 in North Carolina by 12-year-old

Uses of PGEs

Jewelry - durable, strong - artists can create objects that would not be possible with gold - holds hard and crisp lines - holds white color indefinitely - hypoallergenic Autocatalysts - Dominant use of PGEs since 2003 - Used in internal combustion engines - Reduces toxic gases and pollutants in exhaust (improved air quality in many parts of the world) - More PGEs released into environment

Gold - Uses

Jewelry and currency make up 85% of global demand for gold Dental industry (resistant to corrosion/rusting, and is malleable) Electronics (high electrical conductivity)

diamond deposits today

Kimberlite eruptions are no longer occurring. The Earth is no longer hot enough to produce these extremely rapid eruptions. All the diamonds on the Earth's surface today are the only ones that we will ever have access to (unless someone figures out how to mine down to the base of an Archean craton) - we will never make another diamond deposit Luckily for us, we still have lots

Diamond deposits

Kimberlites Lamproites (rarely host diamonds; only important one is in Australia) Placer (historically; all placer deposits have been mined out)

Hydrothermal ore deposits

Largest and most widespread ore deposit forming process Can occur anywhere there is heat and fluids and metal source Hot --> cold facilitates precipitation of metals in liquid As hot fluids flow through the subsurface, they dissolve metals form the rocks (weathering) and transport them to a new place (erosion); metals are precipitated as waters cool (concentrate to form an ore deposit)

Bingham Canyon Mine

Largest human-made excavation in the world (0.6 miles deep and 2.5 miles wide) located in Utah Production since 1906; more copper than any mine in the world (> 19 million tons)

Copper

Latin "cyprium" eludes to ancient source of copper in Cyprus (Cyprus-type massive sulfide deposits) Chemical symbol Cu

Layered Mafic Intrusions (LMI)

Layer: sheet-like accumulation of a mineral that is mineralogically and texturally homogenous PGEs favor staying in the mantle. They bond strongly with sulfide. PGE concentration is 10,000x higher in sulfide magma than silicate magma. Normal magmas are primarily silicate; sulfide minerals are hard to melt and left in mantle. To form LMI, hot spots in mantle allow for extra hot melting where sulfide minerals can melt and contribute to the magma. PGE-/Sulfide-bearing magma cools and crystallizes. Remaining magma becomes unstable w/ respect to sulfide. Sulfide forms immiscible drops (like oil in water). Any PGEs dissolve into sulfide liquid and concentrate into droplets. Droplets eventually sink due to their high density compared to silicate melt. (The liquid mix separates into crystalline minerals and an immiscible sulphide liquid. Just like oil and water, these sulphide droplets can't mix back into the magma as it is cooling and instead scavenging metals such as copper, nickel and PGE as it settles into distinct layers.)

hydrothermal vent origin of life theory

Life began around 3.8 billion years ago. One hypothesis is that life originated at white smokers (sulfates, not sulfides), deep sea hydrothermal vents. Today they are home to extremophile organisms like tube worms and Archaea microbes

mineral resources that are chemical sedimentary rocks

Limestone (cement), gypsum (drywall), halite/salt, iron (steel)

Hydrothermal ore deposit fluids - magmatic water

Magmas can contain about 5% water; bubbles (called vesicles) in lava are formed by volatiles like water vapor escaping when pressure is reduced (not surface or sea water)

Kimberlite volcanoes

Magmas generated at the base of the craton Generated at depths of 125-185 miles Ascend to the surface extremely quickly (over 150 miles/hour) Pick up diamonds (and other rocks) that are in their path along the way (Xenoliths) Kimberlite eruptions are no longer occurring. - The Earth is no longer hot enough to produce these extremely rapid eruptions. - All the diamonds on the Earth's surface today are the only ones that we will ever have access to (unless someone figures out how to mine down to the base of an Archean craton) - Luckily for us, we still have lots

kimberlite volcanoes

Magmas generated at the base of the craton Generated at depths of 125-185 miles mantle Ascend to the surface extremely quickly (over 150 miles/hour) Pick up diamonds (and other rocks) that are in their path along the way

Pegmatites are arguably not ore deposits, but they are still formed by one of the ore-forming process that we learned about. What type of process is responsible for the formation of gemstone-bearing pegmatites? Magmatic Hydrothermal Sedimentary Surficial

Magmatic

Pegmatite zoning - gemstones

Mainly form in miarolitic cavities (aka pockets) near the cores of the pegmatites Pocket environment enables the growth of large, clear crystals

Diamond history - 1st century BC

Mention of diamonds via the word "adamao" in the Mediterranean Roman times: rough diamond set in gold within a tomb of a wealthy young woman - Evidence of diamond's value Diamond carving tools noted in Chinese literature

Largest silver reserves

Mexico and Peru

Top producers of silver

Mexico, Peru, China, Chile/Poland - US is the 10th highest producer

Longwall mining method

Mine the ore, then let the roof collapse More common in modern times, especially in developed countries - Use hydraulic roof supports

De Beers

Mineral claims hotly fought over in South Africa until De Beers Consolidated mines Ltd. was established in 1888 - Single organization controlled the majority of diamond production and sales - Kimberley mine alone produced 250,000 carats/year, increasing to nearly 3 million carats/year in the early 1900s

Beryl

Mineral; Chemical formula: Be3Al2Si6O18 Gemstone varieties = emerald, aquamarine, morganite, heliodor, and others Beryllium (Be) is a "common" incompatible element in pegmatites → beryl is a common mineral in pegmatites Emerald is not found in pegmatites because they don't contain chromium (Cr) and vanadium (V) Most of these colors form when an incompatible element substitutes into beryl's crystal structure in place of aluminum (Al).

Tourmaline

Mineral; Chemical formula: XY3Z6(T6O18)(BO3)3V3W Most of these are not chemical elements (expect O and B) Each of these sites can accommodate various elements (tourmaline is a group of minerals w/ same crystal structure, different elements) "Garbage can" mineral Technically a group of minerals, all with the same structure but different chemistry (39 and counting) Can be every color of the rainbow because its crystal structure can accommodate so many different elements (Same mineral can produce many gemstones) Tourmaline gemstone varieties can be several different colors Many of these colors are similar to other gemstones

Hydrothermal ore deposits - metamorphic water

Minerals w/ water as part of internal structure may be metamorphosed, causing water to separate from the mineral and become liquid water when water molecules separate they can now pick up metals and form hydrothermal ore deposits

Exploration - mining

Mining is very expensive so taking time and resources to explore is important Need to determine the location, size, depth, and the orientation/trend of the deposit How can we tell from this outcrop how big the deposit is? Which direction does it go below the surface? 🡪 If we can figure this out, it will help decide where to mine, what direction to mine in, what technique to use, and the extent of the ore body. Combination of methods: Geologic maps: surface and cross-sectional "Non-invasive" depth studies: drill core

Porphyry deposit formation

Mostly associated w/ oceanic-continental convergent boundaries Mineralization formed by hydrothermal fluids (magmatic + groundwater) Metal-rich fluids flow through cracks and fractures in overlying rock Movement of fluids disperses metals in surrounding rocks forming large alteration haloes (distinct feature)

Myth of superabundance

Myth of superabundance: the idea that our natural resources are so abundant that it doesn't matter how much we use, the planet will continuously replenish the supply Think natural capital - they are our resources to exploit We believe(d) mistakenly, that we would never run out of resources. Stewart Udall

Based on what you about kimberlite volcanoes so far, would you expect them to be associated with a plate boundary, and if so, which type? Yes, a divergent plate boundary. Yes, an oceanic-oceanic convergent boundary. Yes, an oceanic-continental convergent boundary. Yes, a continental-continental convergent boundary. No.

NO

Is diamond an ore? Yes Maybe - some diamonds are and some aren't No

NO

Are kimberlite volcanoes associated w/ a plate boundary?

NO → not related to tectonics

Platinum Group Element, Metal, Mineral ? 6. Au as a naturally occurring native metal

NOT PGE or Platinum group metal/mineral (not PGE - gold)

Copper Age

Native copper is relatively rare Copper ores are quite common Copper can be easily separated from some ores when burned in wood or charcoal fires Smelting: the process of separating a metal from ore by heating and melting People started smelting copper 6000 years ago in Egypt (~4000 BC) Copper smelting started the Copper Age, which lasted ~500 years Mined native copper mines

Mining metals - early history

Native metals (crystals of pure metal) first used Easily mined and separated No refining Copper is the most widely distributed native metal Harder and stronger than other native metals (e.g., gold and silver) Advantage of copper tools rather than stone was apparent to early humans - used in Neolithic times

Problem w/ myth of scientific supremacy

Nature is not only more complex than we know... it is probably much more complex than we can know. We draw links between organisms and food sources, and try to predict feedback loops, but we have no way of knowing how many unknown links and feedbacks exist.

Overhunting of American bison

Near-extinction in late 19th century: Expansion of ranching and farming resulted in habitat loss Industrial-scale hunting by non-Indigenous peoples Increased non-Indigenous demand for hides and meat Deliberate destruction of food source "Every buffalo dead is an Indian gone." - Colonel Dodge, 1867

Tungsten history

No ancient history 1783: Jose and Fausto d'Elhuyar (Spanish scientists) isolated tungsten by reducing tungstic acid in wolframite with charcoal No industrial importance until 1847 when a patent was obtained for to prepare sodium tungstate and create tungstic acid 1904: first tungsten light bulb patented After WWII, market for tungsten carbide opened up due to construction

pegmatite products

Not just gemstones Industrial minerals: quartz, feldspar, micas - High purity quartz (solar applications, fiber optics, lighting), ceramics, glassmaking, pigment, cosmetics Strategic rare metals: lithium (Li), niobium (Nb), tantalum (Ta) - Batteries, jet engine components, superconducting magnets - You can thank pegmatites for your long-lasting cell phone and laptop batteries

Properties of Silver

Occurs naturally as pure silver (native element) but MORE commonly in sulfide minerals (argentite Ag2S, or tetrahedrite) Can form natural metal alloys with gold and copper Similar properties to gold (malleability, conductivity) Dense, but much less dense than gold --> wouldn't get a silver placer deposit Not a "noble metal" (Tarnishes)

Why use an open pit mine?

Open pits are economical when: Large tonnages of reserves are involved (usually low-grade) High rates of production are desired Overburden is thin enough to be removed

Platinum Group Element, Metal, Mineral ? 2. Platinum ring (999 purity)

PGE and Metal NOT mineral - not naturally occurring (ring was made)

Platinum Group Element, Metal, Mineral ? 1. Pt as naturally occurring native metal in nugget form

PGE, Metal AND Mineral

Skaergaard Intrusion

PGE-Au-Ti-V-Fe deposit in SE Greenland Inferred tonnage of 1.5 billion Spatially large with deposits in thin layers Active exploration No mining (yet)

Growing Giant crystals (pegmatites)

Pegmatites contain many incompatible elements such as boron (B), phosphorus (P), fluorine (F), and water (H2O) Act as fluxes - Increase element diffusion rates - Suppress crystal nucleation Number of competing crystal nuclei is reduced Small number of crystals grow to large sizes

Pegmatite mines

Pegmatites form elongated bodies, generally inch to ft scale width Length ranges, but ft to 100s ft scale Small-scale mines Often prospectors, not just mining companies

Top producers of PGEs

Platinum - South Africa, Russia, Zimbabwe Palladium - Russia, South Africa, Canada South Africa (91%), Russia and Zimbabwe have largest PGE reserves

Platinum Group Elements (PGEs)

Platinum called "platina" by Spanish ("little silver") PGEs include 6 elements: Platinum (Pt), Palladium (Pd), Rhodium (Rh), Ruthenium (Ru), Osmium (Os) and Iridium (Ir).

PGEs - History 19th Century to present

Platinum discovered in Russia Significant advancement of platinum metallurgy - Valuable and rare - Used in currency, jewelry, scientific and industrial applications - Pt with minor Ir is reference material for length (1 m) and mass (1 kg) PGEs discovered in South Africa at the Bushveld Complex in 1925 - South Africa dominates global PGE production

Platinum Group Element, Metal, Mineral ? 5. Sperrylite (PtAs)

Platinum group Mineral and contains PGEs, NOT metal (not made up of 100% PGE)

Platinum Group Element, Metal, Mineral ? 4. Pt-Pd alloy, man-made, crystalline

Platinum group elements and metal, NOT mineral (not naturally occurring)

Platinum Group Element, Metal, Mineral ? 3. Pd-Pt alloy, naturally occurring

Platinum group metal AND mineral AND contains PGEs

Massive sulfide silver deposit

Poly-metallic deposits from which silver is mined are not targeted for silver but for Zn, Cu, Pb. Ag is extracted as a byproduct since it is there. Volcanogenic massive sulfide <-- most important Cyprus-type massive sulfide

deposition

Process in which sediment is laid down in new locations

Important trends in the US

Rate of mineral resource use has risen more rapidly than has the rate of population growth. The percentage of mineral resources being supplied domestically has decreased (percentage imported has increased).

Underground Mining Dangers

Rock falls - collapsing roofs Poisonous and combustible gases - no use of gasoline in mines Methane generation - ventilation systems, then used as energy source Coal production has decreased over time; coal miner death

Advantages of surface mining

Safer Less expensive Fewer complications with water, bad air, electricity and falling rock Less regulations The largest mines are usually surface mines - Can produce up to 150,000 tons of ore daily - Heavy machinery and blasting procedures used

Sand and gravel placer deposits

Sand and gravel are important industrial mineral resources. Sand and gravel are clastic sediments, the environment in which they deposit might later be mined for these resources.

Veins

Sheet-like body of crystallized minerals (extends below surface; not just line on surface) Form via precipitation from hydrothermal fluid Associated with a magma body that produces these fluids Fluids utilize existing planes of weakness (fractures and faults) in rock

Photography w/ Silver

Silver halide crystals (AgCl, AgBr, or AgI) suspended in gelatin Crystals sensitive to light (causes chemical reaction) --> produces metallic silver More light (more exposure) --> more silver metal produced

Platinum Group Elements

Similar properties to other transition elements (Ag, Au) Extremely dense (especially Os, Ir, Pt) --> up to 2x as dense as lead Chemical inertness, resistant to corrosion, high melting point, durable, catalyze many chemical reactions (harder to work with because of strength and high melting point, but potentially more appealing for non-corrosive jewelry) much more rare than gold, lead

Gold in placer deposits

Small pieces of gold may deposit with large pieces of sediment (gravel) in streams Gold forms in igneous and metamorphic rocks so parent rock (that was weathered to form placer deposit) has to contain gold

Copper History in US

Small-scale mining extracted copper from high-grade ores Flotation processes allowed large-scale mining to begin in late 1800s - Porphyry ore deposits in Arizona, Montana, Utah - Disseminated ore

Tin

Sn (from Latin "stannum") Does not occur as a native element; most commonly occurs as casserite (SnO2) Also occurs as natural metal alloys, sulfide minerals and rare silicates Soft, malleable, ductile, low melting point, resistant to corrosion Less abundant than copper, more abundant than gold

Tin uses

Solder: used to join pipes, electrical circuits; low MP --> fusible metal alloy (tin and copper) Tin plating: coat that protects other metals; food preservation: tin-plated steel Alloys: pewter, bronze, niobium-tin in superconducting magnets

Gemstone varieties

Some minerals have many different gemstone varieties E.g., the mineral beryl has the gemstone varieties of aquamarine (pale blue), emerald (green), heliodor (yellow), morganite (pink), and more Note the difference between a mineral name and a gemstone name

Overview of history of resource use

Stone Age > Copper Age > Bronze Age > Iron Age > Modern Age To go from one age to the next required greater energy resources, and increasingly complicated ones. Wood > charcoal > coal > oil With these changes comes increasingly complicated and widespread environmental impacts Our modern era began with the industrial revolution, which triggered the need for more coal, iron, and other metals to supply factories and develop cities. This demand created the need for more efficient mining methods and transportation systems. The growth of industry, fed by a growing population, is an upward spiraling process that feeds on itself.

Stone age

Stone Age: first use of minerals (as rocks) From ~2.6 million years ago to ~3300 BC Stone used to make tools Break apart nuts and seeds Grind clay into pigment Spear points to hunt larger game Scrapers to prepare animal hides Awls to shred plant fiber and make clothing

A hypothetical ore deposit begins at 10 ft below the surface and extends to a depth of 50 ft. The ore is concentrated in several thin layers (<1 ft each) that are approximately horizontal and extend laterally for up to 3 miles. Considering all these factors, which method would you choose to mine this deposit? Open pit Strip mining Quarry All three are equally appropriate

Strip mining

Surficial ore deposits

Surficial processes can concentrate elements, making them economical to mine (turn resource --> reserve)

Diamond imitations

Synthetic diamonds up to 25 carats have been created - Chemical composition = C - Companies provide authenticity certificates and ID numbers Common imitations = cubic zirconia (ZrO2), moissanite (SiC) - Lab-grown, though moissanite does occur naturally - Both have higher dispersion than diamond

US Gold Rushes

Tend to rush placer deposits (unlike epithermal, placer deposits are still sediment, not yet hardened rock; need less tools to mine as gold is not bound in rocks but loose and close to surface) Carolina - privately owned land, mined by farmers (1803 - 1820s) Georgia - up to 15,000 miners at peak (1828 to 1840s) California - most famous US gold rush (1848-1855) - 300,000 prospectors - California genocide - 4,500 to 16,000 Native Americans died due to outright killing; thousands more to infectious disease and social disruption by settlers - California became a state due to rapid population increase - San Francisco 49ers

Archean

The Archean is a geologic eon. (An eon is the largest division of time we use)

IR and metal discovery

The Industrial Revolution led to many other metals being discovered and utilized Stainless steel: carbon steel + chromium (Cr) + other metals Ni-steel: military applications - rocket shells, tank armor Ni-Cu: coins (a US nickel is 25% nickel, 75% copper) Aluminum discovered in 1827, but hard to extract Other common steel alloys include cobalt (Co), titanium (Ti), and molybdenum (Mo)

Industrial Revolution

The Iron Age led to the Industrial Revolution (IR), which was fueled by population growth. Rural, agrarian society (make own goods) --> urban, industrial society (others make your goods in factories) Child labor: - ~50% of workers in some British factories in early 1800s under 14 years old - 750,000 children under 15 working in US in 1870 Dangerous and poor working conditions: - Fires, Very low wages (less than half for women and children) - 12-16 hour work days, No paid holidays or vacation - Could be fired if sick or injured Pollution: - Factories spewed smog and soot - Pollutants and chemicals released directly into rivers The overall effects were: People migrated to cities Environmental degradation accelerated In addition, the need for more energy (coal) created a need for better transportation systems Railroads and canals were built

Craton

The ancient core of a continent Archean cratons have been unchanged by plate tectonics since the Pre-Cambrian (at least 544 million years ago) Notice how all the diamond deposits are in Archean cratons...

Iron Age impacts

The demand for iron lead to an energy crisis and forests were cut down to produce charcoal. By the 18th century, England's forests were very depleted, and it threatened England's economy The price index of wood charcoal quadrupled from 1560 to 1660 The price of everything else doubled in the same time span England needed a new source of energy largely to fuel the iron industry Solution = coal Developed as the new source of fuel for iron Allowed more and larger iron production furnaces Putting iron smelters close to coal seams streamlined operations Coal burns hot enough to make cast iron

Pebble Deposit

The largest known undeveloped Cu and Au ore body in the world Located near Bristol Bay --> North America's most productive salmon ecosystem and home to hundreds of species of animals Worth up to 400 billion dollars --> conflicts over if it's worth mining because of the possible environmental effects

Wealth and resources

The majority of human wealth basically comes from agriculture, manufacturing, or mineral resources. Our complex modern society is built around the exploitation and use of mineral and natural resources.

Strength of the rocks and mining

The strength of the rocks being mined is a large determinant in the mining method and type of mining cavern produced. Sedimentary rocks are usually not as strong - roof collapse is a big concern. E.g., coal Need to leave more pillars

qualities that make pegmatites perfect for gemstone growth

These qualities make pegmatites the perfect place to grow gemstones Large crystals Clear crystals Enriched in incompatible elements → these are (often) responsible for color if gemstones - not ores; but pegamatite deposits can be ores

Which of the following is not true regarding pegmatites? They can be enriched in incompatible elements They are igneous rocks They always contain gemstones They can contain rare metals that are used in electronics They can be compositions other than felsic

They always contain gemstones

Economic growth vs economic development

Today's concept of economic growth: in order to grow we must keep consuming To accomplish this requires either Population growth to create more producers and consumers More production and consumption per capita Or both

Tungsten producers

Top producers: CHINA, Vietnam, Russia

Tungsten

Tungsten ("heavy stone" in Swedish) Chem symbol: W from wolfram oes not occur as a native element Most commonly as scheelite [Ca(WO4)] and wolframite [(Fe,Mn)WO4] - Scheelite is fluorescent under short-wave UV light - Used for prospecting; either W or metals associated with scheelite (e.g., gold) Highest melting point of any metal (6192 °F), Extremely resistant to corrosion, Relatively dense (similar to gold), Very hard for a metal Hardness equivalent to silicates Similar abundance in crust to gold

Which method would be most appropriate to mine an orogenic gold deposit? Surface - open pit Surface - strip Underground - tunneling Underground - room and pillar Hydraulic

Underground - tunneling

Sudbury Impact Structure

Unique deposit that supplies a significant portion of global PGEs Meteorite impact crater formed when a large meteorite hit earth 1.5 billion years ago Ni, Cu and PGE deposit

Strip mining

Used where material to be extracted forms a flat lying layer below the surface, with minimal overburden. Generally used for coal.

Uses of Silver

Useful properties: electrical & thermal conductivity, sensitivity. and reflectance to light, malleability/ductility Coinage (mainly historical) Industrial applications (contacts in electrical switches, radio frequency identification devices) Jewelry and silverware (decorative objects due to significantly lower price than gold)

Price of colored diamonds

Weakly colored diamonds are less desirable than colorless diamonds Strongly colored diamonds are more desirable than colorless diamonds - Extremely valuable - Standard price per carat based on color, clarity, and cut does not apply (too rare for standardization) Blues, greens, and reds will fetch the most money per carat

Review: Which of the following factors is not one of the standard factors used to value a diamond? Which company mined the diamond. What color the diamond is. How many imperfections, both internal and external, a diamond has. How well the diamond has been cut. How much the diamond weighs.

Which company mined the diamond.

Is diamond a resource? Yes Maybe - some diamonds are and some aren't No I don't remember what a resource is

Yes

Ophiolite

a section of the Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. obduction (going above continental plate) rather than subduction THIS is how VMS deposits end up on land even though they. formed at oceanic divergent boundaries!

alteration haloes

area around magma where minerals have been altered due to hydrothermal fluid activity

Cut - diamond

certain cuts maximize brilliance and fire (sparkle) - Round Brilliant does this best and is most common - 5 grades from excellent to poor

Carbonate rocks

composed of Co3 2- minerals; formed by sedimentary processes - biological and chemical - limestone and dolostone very reactive

Malachite

copper-bearing gemstone forms when CO2-bearing water interacts with Cu-bearing rocks Gemstone and ornamental material soft --> carving (jewelry, decoration)

Turquoise

copper-bearing gemstone forms when acidic, Cu-rich groundwater reacts with minerals in subsurface containing phosphorus and aluminum gemstone and ornamental material; value based on color and matrix soft --> carving (traditional jewelry of some Native American peoples)

Why does the magma in kimberlite volcanoes have to ascend the surface extremely quickly?

if the process is not rapid, the diamonds will start to convert back to graphite (much more quickly than would happen at the surface of the earth) hot magma will convert diamonds back into graphite

incompatible vs compatible elements - fractional crystallization

incompatible elements stay in the melt (Li doesn't like to be in minerals, would rather stay in magma) compatible elements go into minerals (Si is in many minerals; prefers to go into quartz rather than stay in bulk melt)

Gold's high reflectivity

light hits the material and is immediately re-emitted - longer wavelengths (red, orange, yellow) are better reflected, so pure gold has a reddish hue - blue colors are absorbed (not seen)

Porphyry deposits

magma bodies are felsic porphyritic igneous rocks diverse metal content extremely large (high tonnage; mined as open pits) low to medium grade; average <1% (have to take out a lot of rock to get ore)

Magmatic and hydrothermal ore-forming processes both...

occur in and around magma chambers/volcanoes therefore, location is largely determined by plate tectonic processes (divergent plate boundaries, subduction zones, places where these things have evolved)

porphyry deposit location

oceanic-continental boundaries (contains felsic (light colored) materials from continental crust but requires magma (oceanic --> subduction)

pegmatites are formed by

pegmatites are formed by magmatic deposits (NOT hydrothermal, surficial or sedimentary)

placer vs paleoplacer

placer - still forming (streams where you can pan for gold) paleoplacer - ancient river placer deposit; mine sediment

divergent plate boundary

plates "spread" or move apart lots of volcanoes magma wells up (decompression melting) to fill gap and cools allows for hydrothermal ore deposit formation

fractional crystallization

process in which different minerals crystallize from magma at different temperatures, removing elements from the bulk melt the bulk melt composition changes as crystallization progresses (more/less element relative to other elements changes concentration - M&M activity) some elements are more prone to staying in the liquid/melt than others (crystallized temp = stable temp) (quartz and feldspar persist forever, but metals produced @ a higher temperature are less stable and will change into other rocks via weathering)

erosion

products of mechanical weathering may be picked up and transported

Kimberlite

rare, igneous, ultramafic (very low Si, >18% MgO, high Fe) rock that can contain diamonds and other minerals formed only under very high pressures. Can contain diamonds and other mantle xenoliths Xenolith: country rock that was picked up by the magma Xenocryst: a crystal (such as a diamond) that was formed elsewhere and is transported by the magma

Patina

reaction product that gives a green color to copper that reacts with oxygen - copper oxide, carbonate, sulfide, and sulfate minerals can be done intentionally for aesthetic appeal or because it protects underlying metal from further reactions

continental-continental convergent boundary

regional metamorphism; no magma generation not important setting for ore deposits BUT subduction zones may evolve into cont-cont convergent boundaries so we may find ore deposits formed elsewhere that get displaced and uplifted in the collision (continental drift; ore deposits form at subduction zones and eventually (as all the oceanic plate is subducted), the boundary becomes cont-cont (continental boundary on other side of oceanic)

Laterite soil

rich in iron and aluminum; forms due to prolonged and intense weathering of parent rock rock completely broken down; metals remaining are concentrated

Gold metallic bonding

valence electrons shared throughout the entire material and can move around - electrical conductivity

hot spots

volcanoes independent of plate margins formed by a mantle plume that produce a distinct chain of volcanoes; intra-plate volcanism the hot spot remains stationary as the plate moves over top (explains the chain of Hawaiian islands); we can use this to figure out where new islands will form/which islands formed first/which way plates are moving once magma reaches the seafloor, it burns its way through the crust, forming volcanoes w/o subduction