Minerals & Rocks

Mineral

A naturally occurring, solid, inorganic, and nonrenewable substance that has definite chemical composition and molecular structure (elements make up minerals).

Mineral Characteristics

Based on physical or chemical properties

Ore

A mineral from which a metal can be extracted

Mineral Characteristic: Color

The most visible but very unreliable

Mineral Characteristic: Streak

The colored powder form of the mineral that remains after being scratched on an unglazed porcelain plate; can be a different color than the surface color but is a reliable test for identification

Mineral Characteristic: Luster

The way in which the light is reflected off the surface of the mineral

Metallic Luster

Shines like metals (silver, gold)

Nonmetallic Luster

Vitreous (glass like appearance), resinous, pearly, greasy, glossy, dull, earthy

Mineral Characteristic: Hardness

The mineral’s ability to resist being scratched

How is the relative hardness of a mineral determined?

By comparing it to the hardness of the ten minerals on the Moh’s Scale of Hardness and to the hardness of glass at 5.5

Mineral Characteristic: Cleavage

The tendency of a mineral to split along smooth, flat surfaces

Mineral Characteristic: Fracture

Minerals that do not show cleavage, instead they break unevenly or rough

Mineral Characteristic: Other

Magnetite is magnetic, calcite reacts to hydrochloric acid, and halite tastes salty

Mineral Characteristic: Striations

Parallel straight lines on the surface of a crystal mineral (plagioclase feldspar)

Mineral Characteristic: Dissolution Lines

Fine parallel lines that appear on the cleavage planes

Fluorescence

Some minerals will fluoresce under UV light when energy is absorbed and excites electrons in the molecular structure

Igneous Rock

Formed from the solidification of molten rock material