Eagle Crags: Blue Agate & Bentonite Rockhounding in San Bernardino County, California

Quick details

Access

Permission required

County

San Bernardino County

State

California

Coordinates

35.41457, -117.05522

Geology at Eagle Crags

This spot sits on pyroclastic and volcanic mudflow deposits, unit 8 (Northern Mojave Desert), mapped as rhyolite that formed roughly 23 to 4 million years ago. Volcanic ground like this is where agate, jasper, and other chalcedony typically form, filling old gas pockets and fracture seams in the flow rock.

Mapped unit

pyroclastic and volcanic mudflow deposits, unit 8 (Northern Mojave Desert)

Age

23–4 Ma (Early Miocene to Early Pliocene)

Rock types

rhyolite

Elevation

3,990 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 Eagle Crags

Best months: October to May. Typical highs run 99°F in midsummer and 52°F in midwinter, with winter lows near 27°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, TRONA station (31 mi away), adjusted for elevation.

Land & collecting status

Permission required before collecting

Requires landowner or agency permission before any collecting. Do not enter without explicit authorization.

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 Eagle Crags

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

• Blue AgateEncyclopedia →
• Bentonite
• CalciteEncyclopedia →
• ChalcedonyEncyclopedia →
• JasperEncyclopedia →