Banded blue chalcedony geode

Banded blue chalcedony geodes are characterized by concentric layers of chalcedony often surrounding a crystalline core. Chalcedony is a form of quartz, which can range from translucent to semi-opaque. Typically formed in volcanic rocks, these geodes result from the crystallization of minerals dissolved in water that seeps into the rock. The bluish color results from trace minerals such as cobalt or copper. This specimen was collected in regions where these geological processes are frequent, such as Brazil, Uruguay, or South Africa.

This stone measures approximately 4 cm.