Geology Lab Quiz 1

how are minerals distinguished from one another

based on their unique combo of chemical composition and internal structure (chemical and physical properties)

specific luster

feeling and look

transparent

minerals that are so clear that you can almost read through them

opaque

minerals that do not allow any light to pass through them, even in the thinnest of specimens

uneven fracture

rough, irregular fracture surfaces

conchoidal fracture

smooth curved fracture surfaces, like glass

soft minerals

will not scratch glass, but can be scratched with a knife blade or masonry nail - hardness of 5.5 or less

prismatic cleavage (2)

elongated forms that fracture along short parallelogram cross-sections - 2 cleavages do not intersect at 90 degrees

prismatic cleavage

elongated forms that fracture along short, rectangular cross sections - 2 cleavages intersect at or near 90 degrees ex) potassium feldspar

rock-forming minerals

Minerals that make up most of the rocks of Earth's crust

color

Rocks generally have a 'typical' color. Variations in this color (tarnishing, clarity, weathering) can often help identify a rock.

hackly fracture

breaks along jagged surfaces like broken metal

translucent

let light pass through (non opaque)

density

mass per unit volume (g/cm^3)

fibrous fracture

separates into soft fibers, like cloth

cubic cleavage

shapes made of cubes and parts of cubes - 3 cleavages intersect at 90 degrees - ex) halite

splintery fracture

splinters like wood

striations

straight/fine "hairlike" grooves on the cleavage surfaces or crystal face of some minerals (ex = exsolution lamellae - the mix of light-colored sodium feldspar with darker colored potassium feldspar ex) polysynthetic twinning = parallel, hairline striations on cleavage faces such as with plagioclase feldspar)

crystal

term used when talking about the lattice structure or about mineral specimens that have nicely developed crystal faces

tenacity

the manner in which a substance resists pulling or breaking apart - how a mineral resists breaking - Brittle (shatters like glass), malleable (can be hammered or bent permanently into new shapes like modeling clay or gold), elastic or flexible (like a plastic comb - bends but returns to its original shape) , sectile (can be carved with a knife)

crystal faces

the planar, flat surfaces of a mineral grain that stopped growing when it was still in contact with gas or liquid - orientation of a each face on a mineral grain reflects the orientation of a particular plane in the crystal lattice

crystallography

the scientific study of the structure and symmetry of crystals - concerned with structure, not chemistry

basal (book) cleavage

"books" that split apart along flat sheets ex)talc - but too soft to be visible - 1 cleavage plane

luster

how light is reflects - the appearance of a mineral's surface in reflected light - physical property

fracture

Any break in a mineral that does not occur along a cleavage plane resulting in uneven, random breaks. - broken surfaces, lacking cleavage planes

magnetic

indicates presence of iron (Fe)

good cleavage

results in many small, obvious, flat, stair like parallel surfaces

graphite vs. diamond example

- the unique lattice structure makes the difference between graphite and diamonds - both carbon, but graphite is soft( H of 1) and black and diamonds are the hardest mineral and have a clear color

hard minerals

will scratch glass, but cannot be scratched with a knife blade or masonry nail - hardness of greater than 5.5

streak

• Color of a rock in powdered form. - color of a fine-grained powder of a mineral • Note that a streak plate is 6.5 on the Mohs Scale. --> a mineral with a hardness greater than this will not be able to be streaked on this plate - white plates for dark minerals, dark plates for light minerals - harder minerals can be crushed to a powder or dragged across a diamond file to determine their streak

metallic luster

• Reflect light similar to most common metals. • Opaque, reflective surface with a silvery, gold, brassy, or coppery sheen - light reflects from the outermost surface of a mineral lattice to produce metallic luster, which has a mirror-like quality ex) gold, silver, copper, pyrite, galena

non metallic luster

- Not reflective like metallic, but can still reflect light if a cleavage or habit surface. • Waxy, pearly, earthy, greasy, resinous, vitreous, silky, satin - generally light can penetrate at least a short distance into the crystal lattice before some of it reflects back out again - light can pass entirely through some nonmetallic hand specimens and can through all nonmetallic specimens if they are thin enough

habit

- is the natural shape of a mineral's crystals before any cleavage or fracture occurs.; general crystal forms (geometric shape) and combination • Most of the lab samples do not exhibit crystal forms (the geometric shape of a mineral, formed by intersecting flat, outer surfaces called crystal faces) because they are broken pieces of larger crystals • Unlike the crystal face, the cleavage plane tends to be smooth and shiny - wiry or fillform, twinned, needlike or acicurcular, bladed, radiating needles, fibrous (like asbestos), dendritic, tabular (like a book), botryoidal (grape-like masses with raditing needles inside) - shape of a mineral or of aggregates of the same mineral - shapes in which crystals are commonly found

Flourite

- luster = non metallic - hardness = 4 - cleavage = excellent, octahedral, 4 planes - color = light - purple, white, clear, blue, etc. (colorless, purple, blue, gray, green, or yellow) (transparent or opaque) - streak = white - other properties = variety of colors, oil stain, CaF2 (calcium flouride); crystals usually form cubes (habit); brittle - uses = ore of flourine used in flouride toothpaste, refrigerant gases, rocket fuel

Halite

- luster = non metallic - hardness = 2.5 (<5.5) (2.1- 2.6) - cleavage = cubic; 3 cleavage planes; excellent cleavage in 3 directions that intersect at 90 degrees, so breaks into cubes - color = clear, white, yellow, blue, brown, or red (colorless, white, yellow, blue, brown, or red; transparent or translucent) - streak = white - other properties = cubic habit; salty taste; NaCl; brittle - uses = table salt; road salt; sodium ore; used in water softeners and as a preservative

Calcite

- luster = non metallic - hardness = 3 - cleavage = rhombohedral; 3 planes & angles do not intersect at 90 degrees (3 excellent cleavages) - color = light/white (usually colorless, white, or yellow, but may be green, brown, or pink; opaque or transparent) - streak = white - other properties = reacts with HCl (effervesces); CaCO3 (calcium carbonate) - uses = make antacids tablets, fertilizer, cement; ore of calcium

apatite

- luster = non metallic - hardness = 5 - cleavage = none; conchoidal fracture - color = variety of colors, but often green (pale or dark green, brown, blue, white, or purple; sometimes colorless: transparent or opaque) - streak = white - other properties = hexagonal habit (forms hexagonal prisms) - uses = mostly to make fertilizer, pesticides, transparent varieties sold as gemstones

Gypsum

- luster = non metallic (earthy to pearly for alabaster; silky or satiny for satin spar) - hardness = 2 (very soft) - cleavage = good cleavage in 1 plane; poor cleavage in another plane - color = light (colorless, white, or gray; yellow also for the satin spar variety; transparent to translucent) - streak = white - other properties = soft enough to scratch with fingernail; tabular habit (forms tabular crystals, prisms, blades, or needles - satin spar variety); sulfate (hydrated calcium sulfate) (massive habit for satin spar variety) - uses = plaster-of-paris, wallboard, drywall, art sculpture medium (alabaster)

Talc

- luster = non metallic (silky to greasy) - hardness = 1 - cleavage = poor - does have basal cleavage but so soft it isn't visible (forms cryptocrystalline masses that show no cleavage) - color = light/white (white, gray, pale green, or brown) - streak = white - other properties = soapy or greasy feel, silicate, no habit; can scratch with you fingernail easily; hydrous magnesium silicate - uses = used as a "filler" (to take up space and reduce cost) in plastics for car parts, appliances, massive pieces carved into art sculptures

k-spar, potassium feldspar, orthoclase feldspar

- luster = nonmetallic - hardness = 6 - cleavage = prismatic; two cleavage planes that intersect at 90 degrees (nearly 90 degrees; excellent cleavage) - color = often pink (orange, brown, white, green, or pink; forms translucent prisms with sublateral exsolution lamellae) - streak = white - other properties = exsolution lamellae (in mineralogy, process through which an initially homogeneous solid solution separates into at least two different crystalline minerals without the addition or removal of any materials - makes it appear streaky due to presence of lighter, sodium rich feldspar with that of darker, potassium rich feldspar); silicate (potassium aluminum silicate); KAISi3O8 - uses = used to make ceramics, glass, enamel, soap, false teeth, scouring powders

Quartz

- luster = nonmetallic (greasy) - hardness = 7 - cleavage = none - color = light - many colors (usually colorless, white, or gray but uncommon varieties occur in all colors; transparent to translucent) - streak = too hard to determine (white - but too hard to determine with a streak plate because the hardness is over 6.5, they scratch the streak plate) - other properties = hexagonal habit; conchoidal fracture; SiO2 (silicon dioxide) - uses = as an abrasive; used to make glass, gemstones

Mohs Hardness Scale

A scale ranking ten minerals from softest to hardest; used in testing the hardness of minerals - diamond = hardness of 10 - higher numbered minerals will scratch lower numbered minerals - ranges 1-10 - fingernail = 2. 5 - Copper Penny = 3.5 - Knife/Glass Plate = 5.5 (glass plate - you scratch the mineral to the plate and if it scratches the glass then it is harder than 5.5) - Steel Nail = 6.5 - Masonry drill bit = 8.5

reaction to acid

carbonate minerals react when a drop of dilute HCl (the acid test) is applied to one of their freshly exposed surfaces - carbonate minerals will effervesce (fizz)

minerals

Inorganic, naturally occurring substances with definite chemical composition, distinctive physical properties, and crystalline structure - if you make it, it is not natural and cannot be considered a mineral (this includes usually solids that are generated by biological activity as well) (synthetic crystals are not mineral specimens because they are not formed by geologic processes) - a naturally occurring crystalline solid that has been formed by geologic processes, on Earth or elsewhere in the universe - distinct from one another by their well-defined chemical composition and crystal structure, which result in a unique set of physical properties that can be used to identify it - building block of rocks - physical foundation of both our planet (rock forming minerals) and human societies

submetallic luster

luster that seems intermediate between "metallic" and "nonmetallic"

cleavage

Tendency to break (cleave) along flat, parallel surfaces of weak structural planes. Often results in reflective surfaces/planes - flat surfaces on broken pieces = called cleavage planes & they coincide with surfaces of relatively weak chemical bonding in the crystal lattice - each different set of parallel cleavage planes = cleavage direction

hardness

a measure of a mineral's resistance to scratching - harder substance scratches a softer one

industrial minerals

main non-fuel raw materials used to sustain industrialized societies like ours

no cleavage

no parallel broken surfaces; may have conchoidal fracture (like glass) ex) quartz, apatite

crystalline solid

occur in a regular pattern that is repeated in three dimensions billions of times in even the smallest mineral grain that we can see (a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions)

identification flow chart

primary steps = luster -> hardness -> cleavage & fracture -> color & streak secondary steps = tenacity -> magnetic -> acid test -> habit & crystal form -> smell, taste, feel

mineral grain

refer to a particle composed of a single crystal of a mineral, however we find it - as a singular mineral specimen with well-developed crystal faces, as a broken piece of an individual crystal, as one crystal within an intergrown mass of crystals, or as a rounded sedimentary particle developed from a single crystal of mineral

lattice

regular geometric arrangement of atoms in a crystal - the 3-D geometry of a lattice controls the internal structure and the shape of the outer surface of any crystal

excellent or perfect cleavage

results in a set of obvious, large, flat, parallel cleavage surfaces

poor cleavage

results in a set of small, flat, parallel surfaces that are difficult to detect

dodecahedral cleavage

shapes made of dodecahedrons and parts of dodecahedrons - 6 cleavages intersect at 60 and 120 degrees

octahedral cleavage

shapes made of octahedrons and parts of octahedrons - 4 main cleavages intersect at 71 degrees and 109 degrees to form octahedrons, which split along hexagonal shaped surfaces; may have secondary cleavages at 60 and 120 degrees ex) flourite

rhombohedral cleavage

shapes made of rhombohedrons and parts of rhombohedrons - 3 cleavages do not intersect at 90 degrees ex) calcite

smell and taste

some minerals stand out to the senses