Chalcedony

Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite.

Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. The color of chalcedony sold commercially is often enhanced by dyeing or heating.