Chalcedony

Chalcedony is a cryptocrystalline form of silica, composed of very fine inter growths of the minerals quartz and moganite, these are both silica minerals. Chalcedony has a waxy luster, and may be semi-transparent 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 name is probably derived from the town Chalcedon in Asia Minor. 
Color: White, Black, Grey (blue), Semi Transparent