Looking temptingly like a pink-iced chocolate confection, this mineral assemblage comes from a vein in the Carboniferous Limestone at Merehead Quarry (Torr Works), East Cranmore, in Somerset. The dark brown/ black mineral is largely manganese dioxide (MnO2), the white is calcite (CaCO3), whilst the pink – which forms a thin coating on the calcite crystals – is rhodochrosite (MnCO3), also known as ‘raspberry spar’. Although well-known to collectors for a range of unusual minerals, the output of Merehead Quarry is actually Carboniferous Limestone, of which it produces some six million tons per year.
- Item reference: BRSUG 1299
- Photographer: Simon Powell
- Copyright: Department of Earth Sciences, University of Bristol
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