Where to Find Chalcedony in Montana
Montana has 18 mapped collecting spots that report chalcedony, spread across 12 counties. The largest share sits in Yellowstone County with 4 spots. 16 of the spots are on land mapped as publicly accessible.
Spot list checked against source data on April 1, 2026.
Every chalcedony spot we track in Montana
Best spotAmerican BarLewis and Clark County, MontanaPublic access · Sapphire, Cassiterite, Chalcedony +5
Best spotPryor MountainsBig Horn County, MontanaPermission required · Fossil, Agate, Chalcedony +2- Best spotYellowstone River (Billings area)Yellowstone County, MontanaPublic access · Montana Agate, Chalcedony, Chert +1
Missouri RiverLewis and Clark County, MontanaPublic access · Cassiterite, Chalcedony, Garnet +5
Big Horn CanyonBig Horn County, MontanaPermission required · Agate, Chalcedony, Jasper +2- Jefferson RiverMadison County, MontanaPublic access · Agate, Chalcedony, Jasper +1
- MinerPark County, MontanaPublic access · Agate, Chalcedony, Jasper +1
- Mount BlackmoreGallatin County, MontanaPublic access · Agate, Chalcedony, Hyalite Opal +1
- Yellowstone River - Black Bridge Boat LaunchDawson County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Blue Creek AccessYellowstone County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Bratten Fishing AccessSweet Grass County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Bundy Bridge Fishing AccessYellowstone County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Holmgren Fishing AccessStillwater County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Laurel Sportsman AccessYellowstone County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Myers Bridge AccessTreasure County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Pelican Fishing AccessSweet Grass County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- Yellowstone River - Rosebud AccessRosebud County, MontanaPublic access · Montana Moss Agate, Petrified Wood, Jasper +1
- TerryPrairie County, MontanaPublic access · Petrified Wood, Chalcedony, Jasper
Standout chalcedony spots in Montana
Hand-picked from the full list above, with the reason each one earns a trip.
Pryor Mountains
Big Horn County
The Pryor Mountains stand out for Dryhead-style agate, with Mindat listing agate and chalcedony from the range and a named Dryhead Agate Mine in the Bighorn River area.
American Bar
Lewis and Clark County
American Bar belongs to the upper Missouri River sapphire province, where GIA traces gem-quality sapphire mining back to 1865.
Yellowstone River (Billings area)
Yellowstone County
The Billings reach of the Yellowstone River is a benchmark Montana agate setting, where river gravels carry chalcedony, jasper, chert, and dendritic moss agate.
Best counties for chalcedony in Montana
Ranked by the number of mapped chalcedony spots. County links open the full rockhounding page for that county.
- Yellowstone County4 spots
- Big Horn County2 spots
- Lewis and Clark County2 spots
- Sweet Grass County2 spots
- Dawson County1 spot
- Gallatin County1 spot
- Madison County1 spot
- Park County1 spot
- Prairie County1 spot
- Rosebud County1 spot
- Stillwater County1 spot
- Treasure County1 spot
Before you go
Read the chalcedony identification guide so you know what a keeper looks like in the field: Chalcedony in the encyclopedia.
Chalcedony in Montana FAQ
Where can you find chalcedony in Montana?+
How many chalcedony spots are mapped in Montana?+
Is it legal to collect chalcedony in Montana?+
Where else to find chalcedony
More minerals to hunt in Montana
Hunt chalcedony in Montana with the map in your pocket
RockHoundR puts these spots on an offline map with BLM and Forest Service overlays, geology layers, and a log for your finds.
