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Minerals

Uvarovite, a garnetMinerals are naturally-occurring, solid, inorganic (non-living) substances that consist of chemical elements, such as silicon, oxygen, magnesium and others. Various combinations of minerals make up different types of rocks. For example, the rock sandstone consists mainly of grains of sand pressed and cemented together. Sand is made mainly of the minerals quartz and feldspar. Quartz consists of the chemical elements silicon and oxygen; feldspar is composed of a variety of elements. There are thousands of different minerals, each distinguished by their various chemical and physical properties. A very few kinds—feldspar, mica and quartz, for example—are found in nearly all the Earth’s rocks. 


Hornblende, an amphibole

Amphibole

The amphiboles are a group of silicate minerals, formed from chains of silicon and oxygen atoms, plus a combination of iron, magnesium, sodium, calcium or aluminium. These minerals usually form long, slender, dark-coloured crystals. Amphiboles are found in igneous and metamorphic rocks. A common amphibole is hornblende. Four of the amphibole minerals are commonly called asbestos.
 

The most abundant elements in the Earth’s crust (outer shell) are oxygen and silicon. As a result, silicate minerals (compounds containing silicon and oxygen) are the most common group of minerals: they compose about 90% of the Earth’s crust.

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