Where to Find Agate in Montana

Montana has 10 mapped collecting spots that report agate, spread across 6 counties. The largest share sits in Park County County with 3 spots. 10 of the spots are on land mapped as publicly accessible.

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

Standout agate spots in Montana

Hand-picked from the full list below, with the reason each one earns a trip.

Pryor Mountains
Big Horn County 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. The same Big Horn County country also carries fossil-bearing sedimentary units, so the locality needs careful land-status and fossil-rule checks rather than casual blanket collecting.
Glendive
Dawson County County
Glendive sits in eastern Montana's Yellowstone River agate belt, where gravel bars and nearby breaks are known for agate, jasper, and petrified-wood style silica material. The site earns its place because it represents the downstream end of the Montana agate story, where long river transport has already sorted and rounded much of the collectible material.

Best counties for agate in Montana

Ranked by the number of mapped agate spots. County links open the full rockhounding page for that county.

Every agate spot we track in Montana

Sorted by county. Coordinates open in Google Maps.

Spot	County	Minerals	Coordinates	Access
Big Horn CanyonRoute 211	Big Horn County	Agate Chalcedony Jasper Silicified Coral Fossils	45.3130, -107.9604	Public
Pryor MountainsBad Pass Road	Big Horn County	Fossils Agate Chalcedony Jasper Petrified Wood	45.2386, -108.2675	Public
Bear CanyonBear Canyon Road	Carbon County	Geode Agate	45.0818, -108.5258	Public
GlendiveI 94	Dawson County	Agate Jasper Moss Opal	47.1149, -104.6650	Public
Bakers HoleConservation Lane	Gallatin County	Agate	44.7108, -111.0956	Public
Mount BlackmoreBlackmore Trail	Gallatin County	Agate Chalcedony Hyalite Opal Petrified Wood	45.4447, -111.0035	Public
Jefferson RiverPrimrose Lane	Madison County	Agate Chalcedony Jasper Petrified Wood	45.6902, -112.2745	Public
CarbellaRock Creek Road South	Park County	Agate Jasper Petrified Wood Quartz	45.2175, -110.9273	Public
MinerTom Miner Creek Road	Park County	Agate Chalcedony Jasper Petrified Wood	45.1918, -110.9271	Public
Yellowstone RiverMyers Lane	Park County	Agate Montana Agate Moss Agate Natrolite Silicified Wood	45.6285, -110.5678	Public

Before you go

Read the agate identification guide so you know what a keeper looks like in the field: Agate in the encyclopedia.

Agate in Montana FAQ

Where can you find agate in Montana?+

The mapped spots concentrate in Park County County, Big Horn County County, and Gallatin County County. Every spot on this page appears on the map above with coordinates and access notes.

How many agate spots are mapped in Montana?+

10 spots across 6 counties. The RockHoundR app keeps the same spots on an offline map with public land overlays, geology layers, and your saved finds.

Is it legal to collect agate in Montana?+

Hand collecting of common rocks and minerals in small amounts for personal use is generally allowed on BLM and U.S. Forest Service land, with limits set by the local field office. National parks, most state parks, and tribal land are closed to collecting. 10 of the 10 mapped spots here sit on land marked public. Always confirm current rules with the managing agency before you dig.

Where else to find agate

More minerals to hunt in Montana

Hunt agate 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.