Amethyst Geode with Chalcedony Rim – Unique Piece from Brazil

An amethyst geode with a chalcedony rim from Brazil. A unique specimen with classic two-layer stratigraphy between the microcrystalline outer rim and the macrocrystalline cavity.

The chalcedony rim documents the first mineralization phase of the geode. From a silica-rich solution, microcrystalline quartz aggregates crystallized on the inner geode wall. Only after this did the main amethyst phase follow with macroscopic violet crystals.

The stratigraphy of chalcedony on the outside and amethyst on the inside is a classic two-phase genesis that occurs in many Brazilian geodes. The material differences are clearly visible optically in the polished cut surface.

A well-balanced showcase dimension with clearly readable stratigraphy. An instructive piece for the geode geology of the Serra Geral Formation.