Green Calcite

Calcite occurs in most geological settings and is most common as massive material in limestone and marble; it also forms in hydrothermal deposits. A dealer in Pakistan reported that large quantities of green (and orangy-yellow) calcite were being mined in Baluchistan province. Laboratory records also list translucent light green cat's-eye calcite and bluish-green calcite cabochons from Pakistan.

Like all calcite, it has a Mohs hardness of 3, three directions of perfect rhombohedral cleavage and very strong birefringence (about 0.172), and it fizzes readily in acids, even weak ones such as vinegar. A green calcite cabochon from Pakistan at first resembled opal or chalcedony; testing gave a spot refractive index of about 1.56 with the strong birefringence blink typical of carbonates and a specific gravity of 2.72, it was inert under UV, and it showed wide bands with fine fibrous inclusions. "Mexican Jade" is a misleading name: the material is dyed calcite, not jade. Calcite may be dyed, impregnated with wax or plastic, or irradiated, so a strong colour in inexpensive beads is not by itself proof of natural colour.

Calcite (Mohs 3) scratches easily and splits readily along its cleavage. A care table based on GIA's Gem Reference Guide advises never using ultrasonic or steam cleaners; warm soapy water is usually safe. Keep it away from acids, which make it effervesce, and from high heat, at which it can crack apart (decrepitate). The same table lists natural calcite colours as stable to light.

The mineral name calcite comes from the Latin calx, "lime". Mindat describes it as an ancient name and credits Pliny the Elder (AD 79) with naming it as a mineral. Colour names such as this one are descriptive trade names, not separate mineral names.

The Japanese retailer Pascle writes that stones of the calcite group are said to settle unstable emotions and smooth relationships with other people, and recommends green calcite as a charm for communication.