Meteorites are divided into groups depending on their chemical composition. The three main groups are:
Stones - made of similar minerals to rocks found on Earth.
Stony-Iron - made of a mixture of stone minerals and metal.
Irons - made predominantly of metal (Image shows a 42g part slice of the Gibeon iron meteorite)
Each of these groups is subdivided into two or more meteorite classifications, some of these are detailed in the other sections below. Making an accurate classification cannot be done visually, it requires measuring the relative ratio of several elements/isotopes in the stone. There are a number of lab's around the world who have the experience, knowledge and equipment to make such classifications. Once a stone has been classified, the classification is submitted to the Meteoritical Society. The Meteoritical Society review the classification and, subject to approval, it will be published in the Meteoritical Bulletin. Approval and publication means that the Meteoritical Society committee agrees the scientist performing the classification is qualified to do so and that the classification itself appears reasonable and authoritative.