Calcite belongs to the calcite group, a group of related carbonates that are isomorphous with one another. They are similar in many physical properties, and may partially or fully replace one another, forming a partial solid solution series. All members of the calcite group crystallize in the trigonal subdivision of the hexagonal system (as rhombohedrons and scalenohedrons), have perfect rhombohedral cleavage, and exhibit a strong double refraction in transparent rhombohedrons. Calcite is the one of the most common minerals on earth. It occurs in a seemingly unlimited variety of shapes and colors. It constitutes a major portion of many of the earth's rocks. Calcite's chemical formula is,CaCO3 it has a hardness of 3, and it occurs in all colors, sometimes even multicolored. Its composition consists of, Calcium carbonate, commonly with some impurities of either iron, magnesium, manganese, and occasionally with zinc and cobalt. Among the rocks formed from Calcite are, Limestone, Marble, and Chalk. Calcite, like Aragonite formed from precipitating water that traps in organic matter, such as leaves, twigs, and moss. Also calcareous mounds formed from deposition of hot springs that trap in organic matter. Our calcite specimens are in the form of geodes. The surrounding matix of the calcite crystals is chalk. They were found in the Atlas mountains in Morocco.
