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 thin matrix specimen upon which sit around a hundred calcite prisms. These are scattered around the surface and point randomly in various directions. Most have excellent form and many are partly transparent. Many of the crystals are partially covered by a darker green form of the mineral. Both the white and green forms show the classic vitrous luster. Underneath are numerous spherical formations of black Goethite.

Location: Narakienberg, East Siberia, Russia.