Minerals
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Revision as of 14:56, 1 August 2013
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.
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Classification
Mineralogists and Gemologists classify minerals by 'group', 'species', and 'variety'.
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.
Species
Each specific member of a 'group' is a 'species'.
Variety
Mineraloids
Material found in the earth that originated from living organisms such as amber and jet are called mineraloids.
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.