Onyx

Onyx is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. Sardonyx is a variety with red to brown bands alternated with black or white bands.

The name comes through Latin (of the same spelling), from the Ancient Greek, meaning ‘claw’ or ‘fingernail’. Onyx with pink and white bands can sometimes resemble a fingernail. The English word “nail” is cognate with the Greek word.

Onyx formed of chalcedony bands in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel, unlike the more chaotic banding that often occurs in agates.