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. The most productive ground is in Sweetwater River gravels (Fremont County), Hartville uplift (Platte County), Hat Six area (Natrona County).

Casual hand collection of common rocks and minerals like chalcedony is allowed on most BLM and U.S. Forest Service land in Wyoming, with daily and annual limits set by the local field office. National parks, most state parks, and tribal land are off-limits. Always confirm rules before a trip.

Sweetwater River gravels (Fremont County) is the standout. Other strong ground includes Hartville uplift (Platte County), Hat Six area (Natrona County).