Rauenthalite Phaunouxite

Deep inside the Clara Mine, rainwater slowly seeped through cracks in the rock over millions of years. Along the way it dissolved minerals — and when two different chemical streams finally met in a sealed underground pocket, they reacted and crystallized into something the world had never seen before. Like two ingredients combining to bake a completely new dish. The crystals you see here likely grew over a period of roughly 10,000 to 100,000 years — drop by drop, molecule by molecule, in total darkness.

The formation environment was one of near-total silence — deep underground, sealed from the surface, the only sound an occasional slow drip of water working its way through a hairline crack in the rock. The air would have smelled of cold, damp stone and faint chalk, like the inside of an ancient cellar that has never once been opened.

Rauenthalite is named after its type locality — Rauenthal, a village near Wiesbaden in the Rheingau region of Germany, where the mineral was first described. Phaunouxite takes its name from the Phanou stream near Oulx in the Piedmont region of Italy, the second known locality for the species. Both minerals were formally described from the Clara Mine in Germany's Black Forest, which serves as the world reference site for the pair.

Both rauenthalite and phaunouxite are exceptionally rare hydrated calcium arsenate minerals, with the Clara Mine serving as the type locality for phaunouxite. Co-occurring specimens of both species on a single matrix are virtually unknown outside of this single world-class locality, and their combined scientific significance makes any such piece genuinely exceptional.