chapter 3 physical geology

element abundances in continental crust

27.7% silicon 46.6% oxygen

how many minerals are on earth

4000,

Which of the following is considered a mineral resource? Choose all that apply

A deposit of aluminum four times more concentrated that the average global concentration A deposit of minerals that is not yet economically or technologically recoverable A deposit of copper 100 times more concentrated than the average global concentration

What causes a lack of cleavage in some minerals?

Bonds of equal strength in all directions

Which of the following best describes the term cleavage?

Cleavage is the splitting of minerals along natural planes of weakness

Which of the following exhibits three sets of cleavage at 90° angles?

Galena

Which of the following is a nonsilicate mineral? Choose all that apply

Halite calcite

__________ SiO4 4- tetrahedra join with __________ ions to produce the mineral olivine in the rock peridotite.

Independent; Mg2+ and Fe2+

Silicates

Most important mineral group - Comprise most of the rock-forming minerals - Very abundant due to large amounts of silicon and oxygen in Earth's crust • Basic building block is the silicon- oxygen tetrahedron molecule - Four oxygen ions surrounding a much smaller silicon ion

• Joining Silicate Structures

Most silicate minerals have a net negative charge (except for quartz) - Metal ions are required to balance the charge - These positive ions bond with unshared oxygen ions in the tetrahedra • Most common ions are Fe2+, Mg2+, K+, Na+, Al3+,Ca2+

What is an accurate description of the silicon-oxygen tetrahedron?

The silicon-oxygen tetrahedron is a four-sided figure with a silicon atom in the middle bonded to four neighboring oxygen atoms.

Hornblende has _____ cleavage planes at _____ angles.

Two, non 90

rock

any solid mass of material or mineral like matter that occurs naturally as part of our planet

________ reacts readily with acids such as hydrochloric

calcite

Quartz exhibits ______

conchoidal fracture

What minerals make up half of Earth's crust?

feldspars

Which of the following is an example of a dark silicate

olivine

What are the two most abundant elements in Earth's crust?

oxygen and silicon

• Ionic bonding

pretty weak • Atoms gain or lose outermost (valence) electrons to form ions • Ionic compounds consist of an orderly arrangement of oppositely charged ions

In the list below, indicate which of the items are minerals

quartz gold nugget

the micas (biotite and muscovite) exhibit what type of silicate structure?

sheet

mineralogy

the study of minerals

Important Nonsilicate Minerals

• Divided into groups based on the negatively charged ion or complex ion that the members have in common • Make up approximately 8 percent of Earth's crust

• Chemical bonding

• Formation of a COMPOUND by combining two or more elements

Color

• Generally an unreliable diagnostic property to use for mineral identification • Often highly variable for a given mineral due to slight changes in mineral chemistry • Exotic colorations of some minerals produce gemstones

physical properties of minerals

• Magnetism • Reaction to hydrochloric acid- bubble • Malleability- can you bend • Double refraction- see two things due to light • Taste • Smell-sulfur • Elasticity- bent then bring back to shape

Important nonsilicate minerals

• Many nonsilicate minerals have economic value • Examples - Hematite (oxide mined for iron ore) - Halite (halide mined for salt) - Sphalerite (sulfide mined for zinc ore) - Native Copper (native element mined for copper)

mineral

• Naturally occurring • Inorganic • Solid • Ordered internal molecular structure- atoms all in pattern • Definite chemical composition

mineral resources

• Occurrences of useful minerals ultimately available commercially • Mineral resources include - Already identified deposits that are currently recoverable - Identified deposits that are not yet economically or technologically recoverable

mineral resources

• Ore - A useful metallic mineral that can be mined at a profit - Must be concentrated above its average crustal abundance - Profitability may change because of economic changes

• Specific gravity

• Ratio of the weight of a mineral to the weight of an equal volume of water • Average value is approximately 2.7

hardness

• Resistance of a mineral to abrasion or scratching • All minerals are compared to a standard scale called the Mohs scale of hardness

• Important nonsilicate minerals

• Several major groups exist including - Oxides - Sulfides - Sulfates - Native elements - Carbonates - Halides - Phosphates

• Silicate structures

• Single tetrahedra are linked together to form various structures including - Isolated tetrahedra - Ring structures - Single- and double-chain structures - Sheet or layered structures - Complex three-dimensional structures

atoms

• Smallest particles of matter • Retain all the characteristics of an element

• Cleavage

• Tendency to break along planes of weak bonding • Produces flat, shiny surfaces • Described by resulting geometric shapes - Number of planes - Angles between adjacent planes

Common Silicate Minerals

• The feldspars are the most common silicate group and make up more than 50 percent of Earth's crust • Quartz is the second-most abundant mineral in the continental crust and the only common mineral made completely of silicon and oxygen

• The Light Silicates

- Feldspar group • Most common mineral group • Forms under a wide range of temperatures and pressures • Exhibit two directions of perfect cleavage at !!!!90!!!! degrees • Two most common members: - Orthoclase (potassium feldspar) - Plagioclase (sodium and calcium feldspar)

The Light (Nonferromagnesium) Silicates

- Generally light in color - Have a specific gravity of approximately 2.7 - Contain varying amounts of aluminum, potassium, calcium, and sodium - Lacking iron and magnesium

• The Light Silicates

- Muscovite • Common member of the mica family • Excellent cleavage in one direction • Thin sheets are clear - Used as glass during the Middle Ages • Produces the "glimmering" brilliance often seen in beach sand

Electrons

- Negatively charged particles that surround the nucleus - Located in discrete energy levels called shells

• The Dark (Ferromagnesium) Silicates

- Olivine group • High−temperature silicates • Black to green in color • Glassy luster and conchoidal fracture • Forms small, rounded crystals

• The Dark (Ferromagnesium) Silicates

- Pyroxene group • Important components of dark-colored igneous rocks • Augite is the most common mineral in the pyroxene group - Black in color - Two distinctive cleavages at nearly 90 degrees - Dominant mineral in basalt

• The Light Silicates

- Quartz • Only common silicate composed entirely of oxygen and silicon • Hard and resistant to weathering • Conchoidal fracture • Often forms hexagonal crystals • Colored by impurities (various ions)

• Metallic bonding

- Valence electrons are free to migrate among atoms - Weaker and less common than ionic or covalent bonds

• The Dark (Ferromagnesium) Silicates

- Amphibole group • Hornblende is the most common mineral in this group pretty dark black • Two perfect cleavages exhibiting angles of 120 and 60 degrees

• The Dark Silicates

- Biotite • Iron-rich member of the mica family • Excellent cleavage in one direction - Garnet • Composed of individual tetrahedra linked by metallic ions (similar to olivine) • Glassy luster and conchoidal fracture

The light Silicates

- Clay minerals • "Clay" is a general term used to describe a variety of complex minerals that have sheet structure • Clay makes up a large percentage of soil • Most originate as products of chemical weathering • Kaolinite is common clay mineral used to manufacture fine china

• The Dark (Ferromagnesium) Silicates

- Contain iron and/or magnesium in their structure - Generally dark in color - Have a specific gravity between 3.2 and 3.6

• Joining Silicate Structures

- Covalent silicon-oxygen bonds are typically stronger than the ionic bonds of the silicate structure - Controls the cleavage and hardness of minerals • Examples: - Quartz has a three-dimensional framework, is very hard, and lacks cleavage - Talc has a sheet structure framework bonded with Mg ions and is a very soft mineral

• Fracture

• Absence of cleavage when a mineral is broken

• Luster

• Appearance of a mineral in reflected light • Two basic categories - Metallic - Nonmetallic • Other terms are used to further describe luster such as vitreous, silky, or earthy

Covalent bonding

• Atoms share electrons to achieve electrical neutrality • Covalent compounds are generally stronger than ionic bonds • Both ionic and covalent bonds typically occur in the same compound (bonds are seldom 100 percent ionic or covalent in character) very strong bond Electron is shared

• Elements

• Basic building blocks of minerals • Over 100 known (92 naturally occurring)

• Important nonsilicate minerals

• Carbonates - Primary constituents in limestone and dolostone - Calcite (calcium carbonate) and dolomite (calcium-magnesium carbonate) are the two most important carbonate minerals

Atomic structure

• Central region called the nucleus - Consists of protons (positive charges) and neutrons (neutral charges)

• Streak

• Color of a mineral in its powdered form • Helpful in distinguishing different forms of the same mineral

rock forming minerals

• Composed mainly of the 8 elements that make up over 98 percent of the continental crust 24 common