Stewart Mine: Bismuth Rockhounding in San Diego County, California

Quick details

Access

Public area

County

San Diego County

State

California

Nearest road

Henderson Road

Postcode

92059

Coordinates

33.38128, -117.06225

Geology at Stewart Mine

This spot sits on ground mapped as Granite pegmatite dike that formed roughly 145 to 66 million years ago. Plutonic rock like this weathers slowly into grus and boulders, and the most productive collecting is typically in weathered zones and drainages.

Mapped unit

Granite pegmatite dike

Age

145–66 Ma (Cretaceous)

Elevation

1,010 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 Stewart Mine

Conditions here are workable year-round, with typical highs from 68°F in winter to 88°F in summer.

Climate normals: NOAA 1991-2020 monthlies, FALLBROOK 5 NE station (8 mi away).

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 Stewart Mine

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

• Bismuth