Glass Mountain: Obsidian Rockhounding in Siskiyou County, California

Plan your visit

Generally open to casual rockhounding

County

Siskiyou County

State

California

Coordinates

41.60153, -121.50444

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

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.

Access note: Public obsidian collecting in the broader Modoc and Medicine Lake volcanic area is managed by the Forest Service with site-specific limits and maps. Verify the correct open collecting area and permit requirements before removing material.

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.

Best time to visit Glass Mountain

Comfortable months (45 to 90°F highs)

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.

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.

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