Chap. 2 Minerals2.1 Notes

Properties of Minerals

What is a Mineral? A mineral is a

naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition.

A mineral must have these 5 characteristics

A mineral must be formed naturally.

It must also be inorganic.

A mineral must have a definite chemical composition or range of compositions.

A mineral is always a solid, with a definite volume and shape.

It’s particles must form a crystal (flat sides, sharp edges and corners).

Minerals, Compounds, and Elements

Almost all minerals are compounds (2 or more elements).

Some elements occur in nature in a pure form and not as part of a compound (copper, silver, gold).

Almost all pure, solid elements are metals.

How to identify minerals. Color can be used to

identify only those few minerals that always have their own characteristic color. Ex. Malachite is always green and azurite is always blue.

Mineral identification

The streak of a mineral is the color of its powder. The color of a mineral may vary, but its streak will not.

Luster is another test used to identify minerals. It is the term used to describe how light is reflected from a mineral’s surface.

Mineral identification Each mineral has a characteristic

density. Density = Mass

Volume One of the best ways to identify a

mineral is to test its hardness, using Mohs hardness scale and a scratch test.

Mohs hardness scale 1 = Talc 2 = Gypsum 3 = Calcite 4 = Fluorite 5 = Apatite

(fluorapatite) 6 = Orthoclase 7 = Quartz 8 = Topaz 9 = Corundum 10 = Diamond

....your fingernail has a hardness of 2.5,

....a penny has a hardness of about 3.5,

....glass and a steel nail have nearly equal hardness of 5.5 and

....a streak plate has a hardness of 6.5.

Mineral identification

The crystals of each mineral grow atom by atom to form that mineral’s crystal structure. (known as crystal systems).

Another way to identify a mineral is by the way it breaks apart.

A mineral that splits easily along flat surfaces has the property called cleavage.

Fracture describes how a mineral looks when it breaks apart in an irregular way.

Special Properties of minerals Some minerals can be

identified by special properties. Ex. Magnetism and fluorescence. Some minerals glow under ultraviolet light. They have fluorescence.