Gemstone is a broad term encompassing any mineral that is attractive enough, after being cut and polished, to be used for personal adornment. Precious (gem) and semiprecious (near-gem) are relative terms that distinguish more valuable stones from less valuable stones relative to prevailing markets.

A brief examination of the Geologic Map of Wyoming gives even the casual observer an appreciation for the diversity of Wyoming’s geology. Wyoming hosts some of the best rock exposures in the world, with geologic units ranging in age from more than 3.2 billion years (3.2 Ga) in the early Precambrian (Archean) to less than 1 million (1 Ma) years in the Quaternary. These rocks derive from a wide variety of geologic environments, including sedimentary, volcanic, igneous intrusive, and metamorphic. Varied geology and excellent rock exposures make Wyoming a great place to explore for and collect gemstones.

Wyoming Jade, the Wyoming state gemstone, is the most famous of the state’s geologic treasures. Wyoming also hosts diamonds, corundum (sapphire and ruby), opal, peridot, iolite (gem-quality cordierite), agate, petrified wood, and quartz crystals. Some Wyoming rock types used by lapidaries also include marble, silicified banded iron formation (BIF), fuchsitic quartzite, and gneiss.