MineralsChapter 2 in Review

book,Chapter 4 in

textbook

What is a mineral?• Minerals are naturally

occurring, solid, inorganic compounds or elements.

• Earth’s crust made up of about 3000 minerals.

• Display crystalline structure which means that the atoms are arranged in a regular pattern which is repeated.

Exam

ples

How to identify•Geologists rely on several

simple tests to identify minerals.

•These are based on the mineral’s physical and chemical properties.

•Usually best to use a variety of tests to determine a mineral’s name rather than rely on just one.

Crystal Form•Some minerals are immediately recognizable by their crystal shape.

•Halite (common salt) always occurs in perfect cubes.

•Quartz has double pointed ends and is six-sided .

•Careful, because crystal might be miss formed.

Halite

Qua

rtz

Luster•The way a mineral reflects

light from it’s surface.•Metallic-shiny surfaces

which reflect light, kind of like a chrome bumper on a car.

•Non-metallic luster might be described as dull, pearly, waxy, silky or earthy.

Metallic

Non

-Met

alli

c

Hardness•Hardness is the measure of how easily a mineral can be scratched.

•One of the most reliable tests for identifying a mineral.

•Uses a scale of ten minerals.

Hardness

Cleavage and Fracture

• Atomic arrangement determines how a mineral will break.

• A mineral that splits easily and along flat planes is said to have cleavage.

• Minerals that break along rough or jagged edges are said to have fracture.

Cleavage

Fra

ctur

e

Streak•Streak is the color of the

mineral when it is broken and powdered.

•This test is done by dragging the mineral across an unglazed porcelain plate.

Streak

Streak•Mineral must be softer than plate.

•Some metallic minerals will have different color streak than outside color-hematite.

Color•One of the most noticeable

characteristics.•Some minerals can be a

variety of colors (quartz).•In general, color is the least

reliable clues to a mineral’s identity.

Special properties•Calcite-double vision,

bubbles with acid.•Magnetite-magnetic.•Flourite-glows under a black

light.•Sulfur-bad smell.•Talc-greasy feel.

Texture/ density•Describes how a mineral

feels to the touch.•Smooth, rough, ragged,

greasy or soapy.•Density can be used to

describe various minerals (galena).