Mineral Species: Ankerite and Sphalerite

Chemical Formula: CaFe(CO3)2

Chemical Name: Calcium Iron Carbonate

Mineral Class: Carbonate

Mineral Notes: Ankerite has a very similar structure to Dolomite and forms a solid solution series with the latter mineral, in which Iron replaces Magnesium. Consequently its properties are almost identical, except that Ankerite is usually red-brown whereas Dolomite is normally white. The mineral is usually found in association with iron ore deposits and occasionally in Gold-bearing Quartz veins.

Description: A platy Ankerite matrix which is an epimorph after Barite. On this brown matrix sit numerous small crystals of gemmy, black Sphalerite. The latter have a strong metallic luster which contrasts very strikingly with the underlying matrix.

Location: Admiralty Flat, Nentsberry Haggs Mine, Alston, Cumbria, England.