Great amethyst geode pair with many small white calcite crystals

An amethyst geode pair from Uruguay, in whose violet interior lining small white calcite crystals have grown as a second generation of minerals. An unusual combination in which two minerals have sequentially formed the same geode.

Amethyst crystallized in the original lava geode from silica-rich solutions over millions of years. After this growth process ended, calcium carbonate-containing solutions penetrated the remaining cavity and deposited the calcite scalenohedra over the amethyst tips.

Such multi-generational geodes are didactically valuable: they document that a single cavity structure has accommodated various solution chemistries over long geological periods. The changes between quartz and carbonate solutions typically follow tectonic activity phases.

Uruguayan material from the Artigas Basin is among the most intense amethyst sources worldwide. The combination with calcite crusting increases its collector's value because it incorporates geology as a visible layered narrative.

A collector's item with multi-generational genesis and visually contrasting tension.