Geology Lab Quiz #2 (Minerals) (copy)

Minerals, Moh's scale, crystal habit, uses

Hardness

Measure of relative ability of mineral to resist scratching

Color

The impurities in the mineral determine this

Luster

The reflective ability of a mineral, the way a mineral scatters light

Crystal Habit

The mineral’s shape

Streak

The powdered form of a mineral

Incongruent Streak

Streak color differs from the actual color of the mineral. Example: Chalcopyrite-mineral is shiny gold, yet streaks black

Specific Gravity

The density of the mineral. Example-weight juxtaposed to water

Minerals w/highest specific gravity

Gold-19.32; Lead-11.34; Copper-8.95; Iron-7.8; Galena-7.4

Is Mohs scale of hardness used for rocks or minerals?

Minerals

What minerals on Mohs scale can cut glass?

Minerals w/hardness of 5.5 and greater. Ex: Diamond(10); Corundum(9); Quartz(7); Orthoclase(6)

Minerals used as raw ORE for extracting metals through smelting process

Hematite; Magnetite; Limonite; Azurite; Malachite

Minerals that leave a streak

Ones with hardness less than 7. Ex-Graphite; Talc; Satin Spar; Alabaster

Alabaster

Gypsum/Calcite

Mohs Hardness 2

Forms in layers due to evaporating sea water. Chalky, white color

Uses-sculpting and industrial

Amethyst

• Color: Light to dark purple

• Mohs Hardness: 7

• Transparency: Transparent to translucent

• Specific gravity: 2.6–2.7

• Luster: Vitreous (glassy)

• Crystal structure: Hexagonal, when combined w/rock it makes a geode

• Uses; Jewelry

Amphibole

• Crystal habit: Long prismatic or fibrous

• Mohs hardness: 5–6

• Usually black with straight-line orientation

• Luster: Vitreous, dull, or opaque

• Uses: paving stones and as a veneer or facing on buildings

Apatite

• Color: Usually green but can also be brown, blue, yellow, purple, pink, or colorless

• Mohs Hardness: 5

• Specific gravity: 3.1 to 3.3

• Crystal habit: Elongated, small, hexagonal crystal structure

• Uses: Industrial; fertilizer; or gemstone

Azurite

Color: Azure-blue, deep blue

Crystal habit: Monoclinic

Copper ore

Luster : vitreous

Mohs scale hardness: 3.5 to 4

Specific gravity: 3.773

Uses: jewelry, as an ornamental stone, and as a pigment for painting

Beryl

• Color: green

• Mohs Hardness: 7.5–8

• Luster: Vitreous to resinous /transparent to translucent

• Breaks messily and rarely shows crystal habit. True form hides in rock. Will shatter

• Specific gravity: 2.63–2.92

Biotite

• Color: Black, dark brown, dark green, reddish black, yellow, and white

• Streak: White or gray

• Hardness: 2.5–3 on the Mohs scale

• Transparency: Translucent to opaque

• Luster: Pearly to submetallic

• Specific gravity: 2.7–3.1 g/cm3

• Crystal forms: Thick flakes, micaceous masses, tabular, foliated, flaky, and scaly

• Uses: commercial; paint filler, rubber products, roofing shingles, asphalt

Chalcopyrite

• Color: Brassy to golden yellow

• Hardness: 3.5–4

• Luster: Metallic

• Streak: Greenish black soft & powdery (Incongruent streak)

• Diaphaneity: Opaque

• Specific gravity: 4.1–4.3

• Optical properties: Opaque

• Crystal system: Tetragon

Corundum (Rubies and Sapphires)

• Color: Golden-brown, blue, red, pink, yellow, grey,

• Mohs Hardness: 9 making it one of the hardest minerals

• Streak: White when scratched on a streak plate

• Luster: Adamantine, vitreous, and pearly

• Density: 4.02 g/cm3

• Transparency: Transparent, translucent, opaque

• Tenacity: Brittle

• Parting: Rhombohedral sometimes perfect

• Uses: gemstones, industrial, sandpaper

Flint

• Mohs Hardness 7, can scratch steel.

• Color: Flint can be black, gray, brown, white. Translucent or semi-translucent.

• Concordial fracture, Flint breaks with a glasslike fracture that can produce sharp edges.

• Flint can produce sparks when struck with steel. This property makes it useful for starting fires and making tools.

• Small crystal size makes it tougher than many other rocks and stones.

• Texture: sharp, slick

• Flint also has a waxy or dull luster and can be translucent or opaque. It takes a good polish and then has a vitreous luster.

   

Flourite

• Mohs Hardness: 4 softer than nail

• Light green or purple

• Crystal system: Isometric

• Crystal forms: Cube, octahedron, dodecahedron, tetrahexahedron, trapezohedron, trisoctahedron, and hexoctahedron

• Luster: Vitreous, resinous, or dull

• Specific gravity: 3.2

Garnet

Color: red, burgundy, black or tan Crystal habit: 12 sides, dodecahedron
Mohs Hardness	6.5 – 7.5 (very hard)
Specific Gravity	3.6 – 4.3 (increases with iron content)
Luster	Vitreous (glass-like) to resin-like, transparent to translucent.
Streak	White (or pale shade of sample's color)

Graphite

• Mohs Hardness: of 1–2

• Color: Graphite is dark gray to black, opaque, and shiny.

• Feel: Graphite has a greasy feel and a low specific gravity.

• Structure: Graphite has a hexagonal, multi-layer planar microstructure with alternating layers.

• Metallic and non-metallic properties. Made from carbon just like diamonds, except graphite is made closer to the earth’s surface.

• Uses: Graphite is used in high-temperature lubricants, brushes for electrical motors, friction materials, battery and fuel cells, and pencil "lead". Graphite is also used in furnaces and brake linings.

Halite

• Color: Usually clear or white, but can be red or orange with impurities

• Mohs Hardness: 2.5 (soft)

• Fracture: Conchoidal

• Streak: White

• Luster: Vitreous

• Crystals: Isometric, cubic

• Taste: Salt

• Uses: Rock salt

Hematite

• Mohs Hardness: 5 - 6

• Color: Black to silver gray, in earthy forms is red to brown

• Iron ore

• 1st mineral identified on Mars

• Specific gravity: 5.3 feels heavy

• Streak: Distinctive reddish-brown streak 

• Forms in aquatic environments

Jasper

Mohs Hardness 6.5 -7 will scratch glass

Color: Brown, reddish brown

Crystal habit; hexagonal breaks with a smooth surface can be highly polished

Specific gravity 2.5- 2.9

Uses: ornamentation or as gemstone or items such as vases, seals and snuff boxes

Limonite (Iron Ore)

• Color: Yellow, brown, or reddish-brown

• Streak: Yellowish brown

• Mohs Hardness: 4–5.5

• Luster: Dull, vitreous, or silky porous

• Specific gravity: 2.7–4.3

• Transparency: Opaque

• Fracture: Splintery, uneven

• Tenacity: Brittle 

Magnetite

• Color: Black or brownish-black

• Hardness: 5.5–6.5

• Specific gravity: 5.2

• iron ions

• Lustre: Metallic, sub-metallic

• Streak: Black

• Density: 5.175 g/cm

• Crystal system: Isometric

• Ferromagnetic: Meaning it is strongly attracted to magnetic fields 

Malachite (copper ore)

• Mohs Hardness: 3½ - 4

• Colour: Bright green, with crystals deeper shades of green, even very dark to nearly black; green to yellowish green in transmitted light.

• Streak: Light green.

• Mohs Hardness: 3½ - 4

• Luster: silky, earthy. Transparency: Opaque.

• Patinas in the copper ore is what turns it green, just like the Statue of Liberty because it also is made with Malachite

Milky Quartz

• Silicate dioxide (SiO2)

• Hardness: 7 will scratch glass

• Crystal system: Rhombohedral

• Fracture: Conchoidal

• Luster: Vitreous to greasy

• Streak: White

Muscovite

Form of Mica, sheet silicate

• Color: Usually colorless, white, or silver, but can also be yellow or brown

• Formation: produces thin sheets or flakes

• Mohs Hardness: 2 to 2.5

• Crystal structure: Aluminum silicate sheets weakly bound together by layers of positive ions

• Lustre: Vitreous, silky, pearly

• Transparency: Transparent, translucent

• Streak: white

• Specific gravity: 2.8–2.9 

• Uses: industrial filler, lubricant, electrical and thermal insulator

Olivine

Color: Olive green, yellow green.

Gritty texture

Uses: Industrial abrasives, refractory sand in steel manufacturing

Mohs Hardness	6.5 to 7 (very hard)
Specific Gravity	3.2 (Mg-rich variety) to 4.3 (Iron-rich variety) (average weight)

Orthoclase

Mohs Hardness 6

Color: salmon, peach, cream, tan, beige, white

Texture: high luster, craggly, scraggly look in the shine

Plagioclase

Color: gray, tan, beige, white, cream

Mohs hardness 6-6.5

HIgh luster

Texture: high luster, craggly scraggly look in shine has straight line orientation

Pyrite

Mohs 6- 6.5

Color, brassy gold, shiney, has incongruent black streak

Rock Crystal Quartz

• Chemistry: silicon oxide.

• Mohs Hardness: 7

• Refractive Index: 1.544.

• Specific gravity: 2.65.

• Lustre: vitreous.

Rose Quartz

Mohs 7

Trigonal crystal system

Color: pink

Uses: jewelry and decoration

Satin Spar

Mohs 2, fibrous crystal habit that forms in sticks and can have high luster if not scratched alot.

Also a form of gypsum

Color: milky white or clear

Lustre: vitreous, translucent to opaque. Will dissolve in water

Selenite

Mohs 2

Also a gypsum

Forms in sheets

Has high luster if not scratched alot transparent to translucent

Smokey Quartz

Mohs 7

Color: dark brown

Sphalerite

Crystal habit: dodecahedral. In pure form, it is a semiconductor, but transitions to a conductor as the iron content increases. It’s many facets (flat parts) or “faces” cause it to look glittery.

Color: brown, tan, grey, or black. High luster very shiny

Mohs 3.5 to 4

Talc

Mohs 1 softest mineral

Color: white, milky

Crystal habit: layered and feels very slick

Uses: loose powders for chafing (e.g., talcum powder, baby powder, blush, eyeshadow), and in other forms (e.g., pressed powder, liquid makeup). It is also used in some food items, such as rice and chewing gum, and to manufacture pill tablets.

#1 use is an industrial lubricant. Also absorbs well