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A mineral is a naturally occuring, homogeneous, solid with a crystalline atomic structure. Crystallinity implies that a mineral has a definite and limited range of composition, and that the composition is expressible as a chemical formula. Some definitions of minerals give them as inorganic materials, however both diamonds and graphite are considered minerals, and both are primarily comprised of carbon, which would make them organic. So this leads me, as an engineer, to believe that mineralogists do not have a good, precise definition of a mineral, but rather a loose definition. The definition above, is the most inclusive and would include all substances currently described as minerals. The key items that make something a mineral are occurring naturally, and the definite crystal structure, that is expressible as a chemical formula. Rocks that do not meet this criteria are referred to as amorphis - not having a definite structure or expressible as a chemical formula. Some elements that occur naturally and are minerals are arsenic, bismuth, platinum, gold, silver, copper, and sulphur.

THE DEFINITION OF ORGANIC: Organic chemistry is the study of those substances containing carbon in combination with hydrogen (H), and a few other non metals, namely oxygen (O), nitrogen (N), sulfur (S) and the halogens (F2, Cl2, Br2, and I2).






The mineral, Tourmaline, is widespread and abundant complex boron and aluminum silicate mineral. Tourmalines form slender, three, six, or nine sided prismatic crystals (hexagonal system) in parallel or radiating groups. Hardness is 7 to 7.5, luster is vitreous to resinous, streak is uncolored, and specific gravity is 3.0 to 3.2. The alkali tourmalines, which contain sodium, potassium, or lithium, are pink (rubellite), green (Brazilian emerald), or colorless (achroite), whereas magnesium tourmaline is yellow brown to brownish black (dravite), and iron tourmaline is deep black (schorl).

Color gradation along the lengths of crystals is common, with pink usually found at one end grading into green at the other. Tourmalines develop an electrical charge when heated or deformed, and slabs cut perpendicular to the long axis can polarize light. The best-developed tourmaline crystals are found in granite pegmatites. Crystals are also found in limestones altered by granitic intrusions and, because of high resistance to weathering, in detrital deposits and sedimentary rocks. Transparent colored stones and opaque black crystals are faceted as gemstones. Tourmalines are found on the island of Elba, in Sri Lanka, Madagascar, and the Ural Mountains, and in the state of Maine in the United States.