Minerals are natural occurring, inorganic materials of consistent chemical composition. Usually their atoms are arranged in a definite crystal structure. Most gemstones are minerals. Since they have a uniform chemical composition each mineral has consistent set of physical and optical properties.

Contents 1 Classification 1.1 Group 1.1.1 Garnets 1.2 Species 1.3 Variety 2 Mineraloids 3 Rocks

[edit] Classification

Mineralogists and Gemologists classify minerals by 'group', 'species', and 'variety'.

[edit] Group

Groups can contain two or more minerals with similar properties and structure but slightly differ in chemical properties. For example when one chemical element replaces another in the same formula.

[edit] Garnets

Garnets are classified as a 'group' unlike other families that are classified as a 'species'. This is because the color variations in garnets are due to differences in their actual chemical structure rather then the presence of impurities as in other gem families.

[edit] Species

Each specific member of a 'group' is a 'species' which can then contain numerous 'varieties'. All stones in a 'species' have the same crystal structure and chemical composition and differ only in color.

[edit] Variety

Color variation in the different varieties of a species are caused by the presence of minute impurities.

[edit] Mineraloids

Material found in the earth that originated from living organisms such as amber and jet are called mineraloids.

[edit] Rocks

Rocks are a combination of two or more minerals. Gemstones such as lapis lazuli which is a mixture of lazurite, calcite and sometimes pyrite are classified as rocks.