Calcite

Calcite from Mount Brown, Wollongong, NSW, Australia, measuring 73 × 65 × 15 mm and weighing 96 grams. A broad, flattish plate of crystallised Calcite from the Illawarra region south of Sydney.

Calcite, calcium carbonate CaCO3, is capable of growing in an enormous range of crystal forms, and a specimen of this size and spread is a good demonstration of how varied an otherwise very common mineral can look in hand. Limestone and carbonate-bearing rock through the broader Illawarra district has, at various local workings and exposures, produced Calcite of collector interest, with crystals forming in open joints and cavities as groundwater deposited the mineral over time.

A good, broad Calcite plate like this makes a solid reference specimen for the species, and the locality gives it a specifically New South Wales provenance rather than one of the more commonly seen interstate or overseas sources. This piece is from the Anne McDonald Collection.