Mineral Identification

Properties of Minerals

Luster: The way light reflects from the minerals surface

· can be shiny or dull

· Shiny: metallic luster

Dull: nonmetallic luster

Dull can include: pearly, silky, dull, and greasy

Streak: The color of the powder left on the streak plate

· the streak is always the same even if minerals color differs

· Good way to identify minerals

Color: 1^st property of a mineral most notice

· color is a hard way to identify minerals

most minerals vary in color due to impurities

· Color can tell you about elements in a mineral

Cleavage and Fracture: The two types of mineral breakage

· A mineral that breaks along a flat surface, or plane, has cleavage

· A mineral that leaves an uneven surface when it breaks has fracture.

Specific Gravity: the ratio of a mineral’s density to the density of water

· Water’s density is 1g/cm³

· Most minerals S.G. is between 2-5

· Minerals made mostly of metals usually have higher density

· Heft: used in field to test 2 minerals: compare mass of one with mass of another (2 minerals must have same volume). This is easier to do then specific gravity if you are in the field.

Hardness: The ability of a mineral to resist being scratched.

· Moh’s Scale: Scaled used to test and describe a minerals hardness

* Designed by Friedrich Moh’s in early 1800’s

* He arranged 10 minerals in order of increasing hardness and assigned

them a number from 1-10

* Uses this to find hardness of unknown minerals

Special Properties

Magnetism

· minerals containing iron and nickel are attracted to magnets

· some of these minerals can even act as magnets

Fluorescence

· some minerals will glow when exposed to ultraviolet light

Common Rock-Forming Minerals

· There are thousands of minerals on the Earth

· Only 20 are considered common: Called “rock-forming minerals” because they made up most of the earth’s rocks

· Most are from silicate group: nearly ¾ of the crust is made up of silicon and oxygen!