Agate
Banded chalcedony. The bands record the stone filling its cavity layer by layer, and the cut decides which chapter shows.
Hardness — 6.5 to 7 Care — hard-wearing, everyday Source — Brazil, Botswana
Agate
Chalcedony: quartz grown too fine to see the crystals. It is hard-wearing, takes a high polish, and is the family to choose when a ring will be worn without ceremony.
Dendritic agate
Chalcedony with manganese inclusions that grew in branching patterns. Every stone is a different landscape and no two can be matched as a pair.
Hardness — 6.5 to 7 Care — hard-wearing, everyday Source — India, Madagascar
Fire agate
Chalcedony grown over iridescent layers of iron oxide. Turned in the light it flashes green, gold and red from below the surface; cutting it is slow work done freehand.
Hardness — 6.5 to 7 Care — hard-wearing, everyday Source — Arizona, northern Mexico
Holly blue
Lilac-blue chalcedony from a single district in Oregon, dug decades ago and traded between cutters since. Quiet colour that reads strongest in daylight.
Hardness — 6.5 to 7 Care — hard-wearing, everyday Source — near Holley, Oregon