Great amethyst geode with embedded calcites - cannon spar - from Uruguay

An amethyst geode from Uruguay, with intergrown calcite crystals in the rare cannon spar form. A crystallographically valuable multi-generational constellation.

Cannon spar is a special growth variant of calcite, in which the scalenohedron pyramids are aligned so that they appear like lined-up cannon barrels. A crystallographically defined growth form that arises under specific solution conditions.

The sequence of mineralization can be read from the stone: Amethyst first crystallized in the geode from silica-rich solutions. Only then did calcium carbonate-bearing solutions penetrate and allow the cannon spar calcites to grow as a second generation.

Uruguayan material from the Artigas Basin is considered among the premium deposits worldwide. The association with cannon spar calcites is valued in the collector's trade as a top didactic piece.

A collector's item with crystallographic specialty and multi-generational genesis.