Mineral Species: Dolomite on Barite

Chemical Formula: CaMg(CO3)2

Chemical Name: Calcium Magnesium Carbonate

Mineral Class: Carbonate

Mineral Notes: Dolomite is a common sedimentary mineral that can be found in massive beds, called Dolomitic Limestone. Debate has raged as to how these beds formed. Dolomite at present time, does not appear to form on the surface of the planet; yet thick layers of the mineral can be found in ancient rocks. That poses a huge dilemma for geologists who observe rocks being formed today, why no Dolomite? 

Description: Very rare, individual crystals of brown Dolomite on a twinned crystal of white Barite. The Dolomite crystals are rhombohedral. When magnified some of the crystals can be seen to have curved faces. The mineral has a strong pearly luster, which contrasts very attractively against the white colour and vitrous luster of the underlying Barite.

Location: Ullcoats Mine, Egremeont, Cumbria, England.