Or a mineral is, according to the International Mineralogical Association (IMA)-approved formal defintion (as of 1995), "an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes."
There are over 4,900 known species of minerals. The IMA has approved over 4,660 of them. The study of minerals is called mineralogy.
Minerals can be described and distinguished by various phsyical and/or chemical properties which relate to their structure and composition. Common distinguishing characteristics include: crystal structure and habit, hardness , lustre, diaphneity, color, streak, tenacity, cleavage, fracture, parting and specific gravity. Other properties such as the reaction to acid , magnetism, radioactivity and tase or smell can be used to test minerals.
List of books: Mineral