Purcell-Griffin Mine: Chromite Rockhounding in Mariposa County, California

Quick details

Access

Public area

County

Mariposa County

State

California

Coordinates

37.66225, -120.19561

Geology at Purcell-Griffin Mine

This spot sits on volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains), mapped as mafic volcanic that formed roughly 200 to 145 million years ago. 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

volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains)

Age

200–145 Ma (Jurassic)

Rock types

mafic volcanic

Elevation

1,690 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 Purcell-Griffin Mine

Best months: September to June. Typical highs run 95°F in midsummer and 57°F in midwinter, with winter lows near 35°F. Summer heat here is intense, so carry more water than you think you need and work the early morning.

Climate normals: NOAA 1991-2020 monthlies, GROVELAND 2 station (13 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 Purcell-Griffin Mine

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