very dark Uruguayan amethyst geode

An especially dark amethyst geode from Uruguay, natural in color and form. The rim combines rock crystal and agate into a polished edge, the reverse side shows the original volcanic basalt matrix.

The geode is a gas bubble about 100 million years old from the Cretaceous period. Over millions of years, the amethyst crystals grew inwards from silica-rich solutions.

Uruguay is one of the classic localities for deeply colored amethysts. The dark violet hue is created by iron inclusions and natural radiation within the quartz lattice.

Three characteristics define the piece: strong dark violet color, well-formed geode, visible basalt back as geological evidence.