Calcite CaCO3 Calcium Carbonate
Attributes: Calcite is a common mineral that occurs around the globe. it is one of the main constituents of limestone and marble, and occasionally crystallizes into beautiful forms. Calcite has more uses than almost any other mineral; it is used industrially as an abrasive, construction material, for acid neutralisation, pigment, soil additive, pharmaceuticals and more!
Grades / Identification: Although Calcite is abundant, Calcite Crystals can grow in an aray of forms, some more rare than others. Some higher grade varieties display optical effects such as double refraction. One identifying factor of Calcite is its tendency to luminesce under short or long wave ultraviolet light, another is its perfect rhombohedral cleavage which you may identify where there are fractures on the crystal.
Colours: Most calcite varieties display luminescence when placed under short or long range ultraviolet light. Calcite can be a range of colours including: Transparent (iceland spar), white, blue, pink, yellow, brown, orange, purplish red, tan and grey.
The colouration is due to the presence of metal ions (mostly in transition) or additional minerals within the lattice structure.
- Green colours (often found in Mexico) can originate from the presence of malachite.
- Yellow and brown are due to Iron
- Pink is caused by cobalt
- light purple is caused by manganese (rarest)
- Orange is caused by hematite
Lustre: Vitreous, Sub-Vitreous, Resinous, Waxy, Pearly
Rarity: Faceted gems over 50 carats are rare and worth purchasing and collecting, this is due to the difficulty involved in cutting them. Most abundant carbonate mineral on earth. Most rare colouration is purple.
Growth: Found as veins, ore deposits and as a constituent of marble or limestone rock. Crystals are usually large and transparent. Crystals can grow in many crystallographic forms, including rhombuses to mimic their inner crystal atlas, "Dog tooth" points, hexagonal crystals, stalactites, blades, botryoidal or more.
County of Origin: See Mindat
Hardness: 3 - can be dissolved or will react to weak acids
Chemical Composition: CaCO3 Calcium Calbonate
Crystal system: perfect rhombohedral cleavage in 3 directions. Hexagonal (R) (trigonal).
Health information: When performing lapidary work with calcite it is important to wear PVC gloves, and control dust by keeping your project wet at all times and using grinding wheels with running water attached. If there is any risk of breathing dust, please wear a respirator. With all gemstones, it is important to wear glasses to protect your eyes from flying fragments.
Lore / Ancient Significance: The word "Calcite" came from the 19th century German term "Calcit", which itself came from the Latin word for lime, calx with the added suffix "-ite" which was used to name minerals.