Calcite, Whately quarry.

Calcite, Whately quarry.

Calcite, CaCO3  Calcium carbonate. This specimen is from Whately quarry near Wells in Somerset. The quarry is a limestone quarry, and not surprisingly the most collected mineral from this quarry is calcite. The scalenahedral crystals have developed in a void, and are cream coloured. The orange effect is because the basic crystals have been coated with minute orange coloured crystals. The crystals are based on a bed of massive calcite, which is atop a base rock of hematite.  

Limestone,Landscape marble, Cotham.

Limestone,Landscape marble, Cotham.

Limestone, carbonate rock, Cotham marble var. This is a specimen that should not be in my mineral collection. It could be included in my rock collection, or my fossil collection. It is not a true marble, but a limestone, and is a localised variety restricted to south Wales and west of England  The patterns in this semi polished specimen from Cotham, near Bristol have been created by the upward growth of algae and worms, and are about 200 million years in age.    

Siderite, Lipez, Bolivia

Siderite, Lipez, Bolivia

Siderite,  FeCO3  is an iron carbonate. It has an iron content of 48%, but as it is not found in such great quantities as other iron ores, and is more difficult to process, it has a lower economic value. The crystals are well defined, cream coloured, and rhomohedral. The associated pyrite crystals are much smaller and octahedral. The specimen is from the massive open cast mine in Lipez, Bolivia.  

Pyromorphite, Caldbeck.

Pyromorphite, Caldbeck.

Pyromorphite,  Pb5(PO4)3Cl   is lead chloride phosphate.  One of the secondary lead minerals found in the oxidised zone of lead ore deposits. The hexagonal barrel shaped crystals can vary in shape from thin and elongate, to short and stubby. The colour may also vary, but usually pale green to deep green. This specimen is from Caldbeck in Cumbria, and is a disorganised mass of elongate, pale green crystals.

Azurite, Burra Burra.

Azurite, Burra Burra.

Azurite,  Cu3(CO3)2(OH)2  is a copper carbonate often found in association with malachite, which is chemically similar. Both minerals are found in the weathering zone of copper ores, with malachite being the predominant mineral. The specimen is mostly malachite with inclusions of azurite, both in massive form, and no observable crystals. The specimen was collected at the Burra Burra mine, Burra, South Australia.