Where to Find Chalcedony in Wyoming

Wyoming chalcedony tracks the same volcanic and sedimentary corridors that produce the state's agate. Sweetwater chalcedony, often called Sweetwater agate, is a pink-and-white banded variety from the Sweetwater River gravels in Fremont and Sublette counties. The Hartville uplift in Platte County yields white-to-cream chalcedony nodules in altered limestone, and the Powder River basin in Campbell County adds float chalcedony eroded from old volcanic terranes. The Hat Six area east of Casper produces blue chalcedony in basalt. Most surface chalcedony is small (under fist-size) and concentrated on ranch gravels.

Spot list checked against source data on April 1, 2026.