Gemstones

A gemstone is any mineral that is attractive enough, after being cut and polished, to be used for personal adornment. The modifiers precious (gem) and semiprecious (near-gem) are used to distinguish more valuable stones from less valuable stones relative to prevailing markets.

Faceted pyrope garnets from the southwestern Green River Basin. Photo by Robert W. Gregory.

Wyoming hosts some of the best rock exposures in the world, with geologic units ranging in age from early Precambrian (Archean) to Quaternary. These rocks derive from a wide variety of geologic environments including sedimentary, volcanic, igneous intrusive, and metamorphic. A brief examination of the Wyoming State Geologic Map gives even the casual observer an appreciation for the diversity of Wyoming’s geology. Varied geology and excellent rock exposures make Wyoming a great place to explore for and collect gemstones and interesting rocks.

The best known of Wyoming’s gemstones is nephrite jade or Wyoming Jade, which is the Wyoming State Gemstone. Wyoming also hosts diamonds, corundum (including sapphire and ruby), opal, peridot, iolite (gem-quality cordierite), and numerous quartz family gemstones such as agate, petrified wood, and quartz crystals.

The collection and marketing of small quantities of gemstones and unique geologic materials is not tracked in Wyoming. Amateur collectors, prospectors, semi-professionals, and professional dealers sell these materials primarily at gem and mineral shows, in local jewelry and rock shops, and over the internet. These mineral commodities include nephrite jade, ruby, sapphire, iolite, kyanite, opal, quartz, jasper, many varieties of agate, satin spar, and labradorite. Kimberlite, lamproite, and other rock specimens are sold under similar conditions.

Exploration for commercial gemstone deposits has increased in recent years, and has focused on diamonds, iolite, ruby and sapphire, opal, and jade.

Additional Information:

Wyoming Jade Diamonds
Wyoming Jade Habitat of Opal Presentation Diamonds

Recommended Reference Material

Further information on most of Wyoming’s gemstone deposits can be found in the following WSGS publications:

WSGS Bulletin 71, Gemstones and other unique rocks and minerals of Wyoming, by W. Dan Hausel and Wayne M. Sutherland, 2000, 268 p.

WSGS Bulletin 72, Minerals & Rocks of Wyoming, by W. Dan Hausel, 2005, 160 p.

A comprehensive summary of the geology of Wyoming, helpful in understanding Wyoming’s gemstone deposits, is found in:

WSGS Memoir 5, Geology of Wyoming, edited by Arthur W. Snoke, James R Steidmann, and Sheila M. Roberts (1993), 937 p.

Additional overviews of Wyoming’s geology are found in:

WSGS Bulletin 67, Traveler’s guide to the geology of Wyoming, by Donald L. Blackstone, Jr., 1988, 130 p.

USGS, Geologic Map of Wyoming, by J.D. Love, and A.C. Christiansen, 1985, scale 1:500,000.

For a complete listing of WSGS materials, go to the Online Store.