Alum Rock Park: Albandite & Hausmannite Rockhounding in Santa Clara County, California

Updated June 2026

Alum Rock Park is a mapped rockhounding spot in Santa Clara County, California. Reported finds include albandite, hausmannite, tephroite. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Santa Clara County
State: California
Nearest road: Penitencia Creek Trail
Postcode: 95127
Coordinates: 37.39579, -121.80192

Geology at Alum Rock Park

This spot sits on ground mapped as Alluvium, undivided that formed within roughly the last 3 million years. Loose deposits like these are float-collecting ground: erosion keeps moving durable rocks and minerals into gravel bars, cutbanks, and washes.

Mapped unit: Alluvium, undivided
Age: 3 Ma to present (Quaternary)
Elevation: 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 Alum Rock Park

Conditions here are workable year-round, with typical highs from 57°F in winter to 80°F in summer.

Climate normals: NOAA 1991-2020 monthlies, SAN JOSE station (7 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 Alum Rock Park

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

Nearby rockhounding spots

Other rockhounding spots within driving distance of Alum Rock Park.

Alum Rock Park FAQ

Where is Alum Rock Park?+

Alum Rock Park is in Santa Clara County, California, at 37.39579, -121.80192. Nearest road: Penitencia Creek Trail.

What rocks and minerals can you find at Alum Rock Park?+

Alum Rock Park is reported to produce Albandite, Hausmannite, Tephroite.

Is collecting allowed at Alum Rock Park?+

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. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Alum Rock Park?+

A rock hammer, sturdy gloves, safety glasses, and a collecting bag cover the basics here. Add a spray bottle: wet rock shows color and pattern that dry rock hides.

When is the best time to visit Alum Rock Park?+

Alum Rock Park is workable year-round.

How do I get to Alum Rock Park?+

Open the directions link to navigate to 37.39579, -121.80192 in Google Maps. The nearest road is Penitencia Creek Trail.

More rockhounding in California

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Open Alum Rock Park on the map

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