Horse Mt (West Side): Epidote Rockhounding in Humboldt County, California

Quick details

Access

Public area

County

Humboldt County

State

California

Coordinates

40.87347, -123.74325

Geology at Horse Mt (West Side)

This spot sits on Ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains), mapped as peridotite and serpentinite that formed roughly 1000 to 175 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 2 (Western Sierra Nevada and Klamath Mountains)

Age

1000–175 Ma (Neoproterozoic to Early Jurassic)

Rock types

peridotite and serpentinite

Elevation

4,380 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.

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 Horse Mt (West Side)

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

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