Minerals

Minerals
A mineral is a naturally occurring chemical compound. Most often, they are crystalline and abiogenic in origin. A mineral is different from a rock, which can be an aggregate of minerals or non-minerals and does not have one specific chemical composition, as a mineral does.

The study of minerals is called mineralogy. There are over 5,300 known mineral species. The silicate minerals compose over 90% of the Earth's crust.

Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification.
The general definition of a mineral encompasses the following criteria:
Naturally occurring
Stable at room temperature
Represented by a chemical formula
Usually abiogenic (not resulting from the activity of living organisms)
Ordered atomic arrangement

Mineral classes
As the composition of the Earth's crust is dominated by silicon and oxygen, silicate elements are by far the most important class of minerals in terms of rock formation and diversity. However, non-silicate minerals are of great economic importance, especially as ores.

Rocks, ores, and gems
A rock is either an aggregate of one or more minerals, or not composed of minerals at all.

In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals.

There are about 20 mineral species that qualify as gem minerals, which constitute about 35 of the most common gemstones.