Best spot

Glass Mountain: Obsidian Rockhounding in Siskiyou County, California

Updated June 2026

Glass Mountain represents California's northern volcanic-glass collecting better than any ordinary agate wash, with Forest Service materials identifying designated obsidian collecting areas in the Modoc country. Mindat's Siskiyou County records place Glass Mountain and Little Glass Mountain among mapped pumice and obsidian-related localities, tying the material directly to young Cascade volcanism. Reported finds include obsidian. Below: coordinates, access notes, nearby spots, and trip-planning links.

Glass Mountain photos

Public image records connected to this spot or its reported material.

2 photos

Quick details

Access: Public area
County: Siskiyou County
State: California
Coordinates: 41.60153, -121.50444

Geology at Glass Mountain

This spot sits on Recent (Holocene) volcanic flow rocks, unit 1 (Cascade Volcanic Field), mapped as dacite and andesite that formed within roughly the last 3 million years. Volcanic ground like this weathers into rocky slopes and float, and fresh exposures in cuts and drainages are usually the most productive places to look.

Mapped unit: Recent (Holocene) volcanic flow rocks, unit 1 (Cascade Volcanic Field)
Age: 3 Ma to present (Pleistocene to Holocene)
Rock types: dacite and andesite
Elevation: 7,610 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Best time to visit Glass Mountain

Best months: April to October. Typical highs run 76°F in midsummer and 33°F in midwinter, with winter lows near 13°F. At about 7,610 ft, snow can block access from late fall well into spring, so check conditions outside of summer.

Climate normals: NOAA 1991-2020 monthlies, LAVA BEDS NAT MON station (8 mi away), adjusted for elevation.

Land & collecting status

Generally open to casual rockhounding

Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

State guidance last verified: April 1, 2026

BLM California — Recreational mineral collecting
California Geological Survey
CDFW — Suction Dredge Mining Permit Program
Community submissions reviewed against published agency rules

Found at Glass Mountain

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

Obsidian Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Glass Mountain.

Across the state line from Glass Mountain

Glass Mountain is close enough to the California border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Glass Mountain FAQ

Where is Glass Mountain?+

Glass Mountain is in Siskiyou County, California, at 41.60153, -121.50444.

What rocks and minerals can you find at Glass Mountain?+

Glass Mountain is reported to produce Obsidian.

Is collecting allowed at Glass Mountain?+

Generally open to casual rockhounding. Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Glass Mountain?+

A rock hammer, sturdy gloves, safety glasses, and a collecting bag cover the basics here. Add a spray bottle: wet rock shows color and pattern that dry rock hides.

When is the best time to visit Glass Mountain?+

The most comfortable months at Glass Mountain are April to October. At about 7,610 ft, snow can block access from late fall well into spring, so check conditions outside of summer.

How do I get to Glass Mountain?+

Open the directions link to navigate to 41.60153, -121.50444 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in California

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Open Glass Mountain on the map

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