Where to Find Agates in Montana: 16 Mapped Sites
Montana has 16 documented sites where agates have been reported, and the best-known are Big Horn Canyon, Pryor Mountains, and Yellowstone River. Every site is mapped below with GPS coordinates and links to a full report of access and what's been found there. 16 of the 16 sites are on public-access land.
Last updated: — data compiled by the Rockhounding.org Research Team · methodology
Agates Map: Montana
All 16 agates sites in Montana. Click a pin for the full site report.
Where Agates Are Found in Montana
Agates fill gas cavities in old lava flows, then outlast the host rock and concentrate in gravels. Hunt gravel bars, beaches, glacial till, and desert washes rather than solid outcrop.
The richest reported sites in Montana: Big Horn Canyon, Pryor Mountains, Yellowstone River, Carbella, Jefferson River.
Local reporting distinguishes Montana Agate (7 sites), Moss Agate (2 sites).
Of the 16 sites, 16 are public access. Check each site report for current land status before you go.
All Agates Sites in Montana
- Big Horn Canyon — Public Access
- Pryor Mountains — Public Access
- Yellowstone River — Public Access
- Carbella — Public Access
- Jefferson River — Public Access
- Miner — Public Access
- Mount Blackmore — Public Access
- Yellowstone River (Billings area) — Public Access
- Glendive — Public Access
- Bear Canyon — Public Access
- Cracker Box Creek — Public Access
- Custer County — Public Access
- Fallon — Public Access
- Hatchet Creek — Public Access
- Hysham — Public Access
- Sand Creek — Public Access
How to Identify Agates
Agate is banded chalcedony: a waxy-luster stone, hardness about 7, that breaks with a smooth conchoidal (shell-like) fracture instead of splitting on flat planes. The reliable field test is backlighting — hold a wetted stone to the sun and an agate glows translucent at the edges, usually showing its bands. Jasper looks similar but stays opaque.
Not sure what you found? Try our identification guide →Frequently Asked Questions
Where can I find agates in Montana?
Montana has 16 mapped sites where agates have been reported. The best-known are Big Horn Canyon, Pryor Mountains, and Yellowstone River. Each listing on the map above includes GPS coordinates, access type, and what has been found there.
How many agates sites are mapped in Montana?
We have 16 documented agates sites in Montana, compiled from community submissions and published locality records and reviewed by the Rockhounding.org Research Team.
Is it legal to collect agates in Montana?
Casual collecting is generally allowed on BLM and National Forest land for personal, non-commercial use — the standard BLM limit is 25 lbs per day plus one specimen. National parks, monuments, and many state parks prohibit collecting, and private land always requires the owner's permission. Check the site report for each location and verify current land status before you dig.
How do I identify agate?
Agate is banded chalcedony: a waxy-luster stone, hardness about 7, that breaks with a smooth conchoidal (shell-like) fracture instead of splitting on flat planes. The reliable field test is backlighting — hold a wetted stone to the sun and an agate glows translucent at the edges, usually showing its bands. Jasper looks similar but stays opaque.
What kinds of agates are found in Montana?
Reports from Montana distinguish Montana Agate (7 sites), Moss Agate (2 sites).
What should I bring to collect agates?
The basics: a rock hammer, safety glasses, gloves, a bucket or padded bag for specimens, and a GPS app with the coordinates from this page. Add a spray bottle — wetting a stone makes color and banding far easier to judge in the field.
⚠️ Always verify current regulations, weather conditions, and access requirements before visiting any location. Information provided is based on community submissions and may not be current or accurate.
Agates in Nearby States
Data: community submissions — reviewed and approved by the Rockhounding.org Research Team. Always verify current land status, regulations, and access before visiting any site.