Blue Calcite

Calcite occurs in most geological settings and is most common as massive material in limestone and marble; it also forms in hydrothermal deposits. Blue calcite studied in 2026 came from Inner Mongolia, China (obtained from dealers); vesuvianite inclusions suggested a skarn-type origin. Blue calcite from Central Anatolia (Turkey) and Madagascar has also been studied, and a blue cat's-eye calcite from Myanmar is on laboratory record. Pascle, a Japanese retailer, says vivid translucent and milky pale types come from different localities.

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. Blue calcite from Inner Mongolia showed weak blue-violet luminescence under UV light and a broad emission band near 480 nm under 405 nm excitation, with no transition-metal absorption peaks. 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 blue calcite as a charm for communication.