Minerals Chapter 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. Halite, Calcite, Olivine, Sulfur, Galena, Feldspar, Quartz, Examples

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 Quartz

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-Metallic

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 Fracture

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

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).