Among Colorado minerals that generate a high dollar volume are varieties of cryptocrystalline quartz. In its various forms, this mineral is known as carnelian, chalcedony, onyx, sardonyx, chrysoprase, agate, jasper, petrified wood and many others. It is found in many locations around the state, with petrified (agatized) wood occurrences in Arapahoe, Douglas, Elbert, Delta,and El Paso counties (to name a few).

Sow belly agate from the amethyst vein of the Commodore mine in Creede.

Sowbelly agate from the Last Chance Mine. Creede District, Mineral Co., Colorado. The term “sowbelly” refers to cryptocrystalline quartz consisting of alternating bands of chalcedony and amethyst and which may contain native silver.