Calcite

Calcite from the Grabiszyce Basalt Quarry, Lower Silesia, Poland, measuring 71 × 48 × 47 mm and weighing 139 grams. A good solid piece from one of Poland's basalt-hosted mineral localities.

Calcite, calcium carbonate CaCO3, is one of the most form-variable minerals known, and at Grabiszyce it formed within gas cavities in Cenozoic basalt, the kind of setting that, in basalt provinces elsewhere in the world, more commonly produces zeolite-group minerals; late-stage, low-temperature groundwater moving through the cooling lava deposited Calcite in the same cavities instead of, or alongside, species such as those seen in the better-known Indian and Victorian basalt fields.

Lower Silesian basalt minerals are collected far less widely outside Central Europe than their Indian or Victorian counterparts, making a Grabiszyce Calcite a point of difference for a broader basalt-mineral suite. This piece carries a double provenance, the David Vince Collection and Pristine Minerals.