Benitoite Gem Mine: Rockhounding in San Benito County, California

Quick details

Access

Paid / fee dig

County

San Benito County

State

California

Nearest road

Sawmill Creek Road

Coordinates

36.33676, -120.60644

Geology at Benitoite Gem Mine

This spot sits on Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains), mapped as serpentinite that formed roughly 175 to 145 million years ago. Metamorphic rock like this weathers into resistant float, and minerals that survive transport typically concentrate in nearby drainages.

Mapped unit

Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains)

Age

175–145 Ma (Middle Jurassic to Late Jurassic)

Rock types

serpentinite

Elevation

4,560 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 Benitoite Gem Mine

Conditions here are workable year-round, with typical highs from 51°F in winter to 88°F in summer.

Climate normals: NOAA 1991-2020 monthlies, PRIEST VALLEY station (11 mi away), adjusted for elevation.

Land & collecting status

Pay-to-dig site

This is a fee-dig location. Hours, prices, and what you can keep vary by operator. Call ahead before driving out.

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