updated in 2018
Calcite is a common substance in the earth, most notably it is the primary component of limestones and marbles. Limestone is the sedimentary rock that were created when the calcium carbonate/skeletal remains of marine organisms were deposited on the ocean floor.
Calcite can be completely transparent (colorless), translucent or whitish. Coloring of calcite is a product of other mineral impurities. For example iron oxide (rust), known in the mineral world as Hematite, can give calcite crystals a reddish tint. In addition to red, calcite has been found in yellow, orange, blue, green, brown, grey, etc
Over 800 forms of calcite crystals have been described. Common forms of calcite crystals are rhombohedron, scalenohedron and prismatic (elongated in one direction). Calcite crystals can also be found as tabular or acicular (a radiating mass of slender, needle-like crystals); twinned calcite crystals are very common.
Calcite is a highly collected mineral but it must be handled with some care. Relatively soft, it is possible to scratch Calcite with a fingernail.
Hardness - 3
Chemical Class - Carbonates
Crystal System - Trigonal, Class - Hexagonal Scalenohedral