Amethyst pair with great agate rim and star-shaped calcite

A large pair of amethyst geodes from Brazil with a distinct agate rim and several calcite stars inside both halves.

Calcite stars form when calcite crystallizes from residual solutions in a six- to seven-rayed arrangement as a later mineralization phase after amethyst growth. They are a rare growth form and are particularly sought after by collectors.

Amethyst belongs to the quartz family and crystallizes in the volcanic gas cavities of lava flows. The violet color is caused by tiny traces of iron in the crystal lattice under natural radiation over millennia.

The wide agate rim (white to light grey-blue banding) shows the mineralization history from the outer volcanic rock to the inner amethyst crystal field.

What makes this pair special is the trio mineralization: agate rim, amethyst crystal field, and calcite stars, three clearly separated phases in a single piece.

A collector's item of the highest class, suitable as a central composition in a living room or a collector's display case.