Cacholong

What is cacholong?

Cacholong, also spelled cacholong opal, is a traditional decorative name for an opaque white to cream variety of common opal. It is a mineraloid rather than a fully crystalline mineral, so it does not have a fixed crystal system or a single strict set of mineral properties.

Material and appearance

The material is usually milky white, bluish white or cream, sometimes with a faint opalescent or porcelain-like look. It can contain brown, grey or black dendritic markings from iron and manganese oxides. Unlike precious opal, cacholong is valued mainly for its quiet opaque colour rather than a strong play of colour.

Formation and localities

Common opal can form when silica-rich water deposits hydrated silica in shallow hydrothermal settings, cavities or weathering zones. Cacholong has been reported from Central Asia, Kazakhstan, Mongolia, Iceland and Russia, among other localities.

Use in mosaic

Cacholong provides soft whites and warm cream tones in a stone composition. It is useful for petals, highlights, clouds and pale backgrounds, where its natural texture is gentler than a uniform artificial white.