Agate, Carnelian & Onyx (Chalcedony)

These are varieties of chalcedony - cryptocrystalline quartz composed of submicroscopic fibres. Agate is characterised by concentric, curved colour banding. Carnelian is a translucent, brownish-red to bright orange chalcedony coloured by iron oxide. Onyx features flat, parallel colour banding (typically black and white), which has made it the historical material of choice for carving cameos and intaglios.

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