Calcite

Calcite from Pachapaqui, Ancash, Peru, measuring 86 × 54 × 43 mm and weighing 182 grams. A well-formed piece from a Peruvian locality known among collectors chiefly for its base-metal sulfides, here represented instead by its gangue mineral at its best.

Calcite is calcium carbonate, CaCO3, one of the most common minerals on Earth, but also one of the most variable in crystal form, capable of growing as scalenohedra, rhombohedra, tabular plates and much more besides depending on the conditions it grows under. Pachapaqui's deposit is a polymetallic zinc-lead-copper-silver orebody in the Peruvian Andes, and its veins and skarn zones have produced well-crystallised Calcite alongside the Sphalerite and Pyrite the mine is more commonly known for, with the Calcite often forming after the main phase of sulfide deposition in spaces the earlier minerals left open.

Peru's base-metal mines are collected first for their sulfides, which makes a genuinely well-formed Calcite specimen from a locality like Pachapaqui a less expected find, and one that rewards a closer look at the mine's full mineralogy rather than just its headline species. This piece is from the David Vince Collection.