Agate / Crystal Geode

Halves of a split stone, each with a lilac ruffle around a dark hollow.

This is an agate and crystal geode. A geode is a hollow rock lined with mineral crystals, and it forms when mineral-bearing water slowly deposits material inside a cavity over a very long time. Matched pair of oval cut faces in pale grey-blue. A band of purple, granular points rings a small dark cavity in each half, edged by a thin tan rind. The cut surfaces are smooth and softly glossy. It is 5.5 inches wide, 4 deep and 3.5 high.

Nature's idea of a secret, politely cut open.