Amethyst with white clear calcite crystals

An amethyst geode from Santa Catarina, Brazil, with clear white calcite crystals growing as a second generation on its violet inner wall. A two-mineral genesis with clear visual stratigraphy.

Amethyst first crystallized in the lava geode from silica-rich solutions. Only after this phase was completed did calcium-carbonate-bearing solutions penetrate the remaining cavity, allowing the calcite scalenohedra to grow as a later generation.

The calcite crystals visible here show the trigonal scalenohedral form typical of carbonates, with clear longitudinal striations. Their clarity indicates a pure, undisturbed crystallization phase.

Santa Catarina in southern Brazil is an established amethyst deposit. The association with clear calcites is valued in the collector's trade as a didactic multi-generational piece.

A collector's item with clear mineralogical stratigraphy.