Calcite, CaCO3 (Calcium Carbonate), is one of the commonest minerals, being the main constituent of limestone. Calcite is often fluorescent, a small amount of Managnese is enough to make it glow red under UV light. The mineral will bubble in acid distinguishing it from many similar species, even other carbonates which do not dissolve so easily in cold acids.

Description: A very large single crystal of calcite having a hexagonal cross-section and a perfect termination. Whilst the outside edges are transparent, the interior is coloured red and brown by inclusions of hematite. This makes for a very showy specimen. Two smaller crystals attached at the sides complete the ensemble.

Location: Guiyang, Hunan, China.