Calcite

Calcite from the North Mine, Broken Hill, N.S.W., Australia, measuring 58 × 54 × 41 mm and weighing 101 grams. A compact, well-formed specimen from one of the historic mines on the famous Broken Hill line of lode.

Broken Hill is one of the world's great lead-zinc-silver orebodies, a Proterozoic deposit that was later caught up in regional metamorphism so intense that it recrystallised the ore and its surrounding rock into coarse, often spectacular mineral assemblages rather than leaving the original sulfides undisturbed. Calcite is one of the more straightforward species to come out of that process, calcium carbonate crystallising in open spaces within the lode and its associated rock, but a clean, well-formed piece like this still represents the same geological history that produced Broken Hill's much rarer manganese minerals.

The North Mine was one of the principal producers along the line of lode through the twentieth century, and specimens from it carry the weight of a deposit that has been mined continuously since 1883 and is still, after more than a century, one of the most studied orebodies in the world. This piece carries a double provenance, the David Vince Collection and the Ruth Coulsell Collection.