Mt. Gilboa: Axinite & Prehnite Rockhounding in Hunterdon County, New Jersey

Plan your visit

Generally open to casual rockhounding

County

Hunterdon County

State

New Jersey

Nearest road

Daniel Bray Highway

Postcode

08530

Coordinates

40.38978, -74.95619

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

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.

Best time to visit Mt. Gilboa

Comfortable months (45 to 90°F highs)

Best months: March to December. Typical highs run 87°F in midsummer and 41°F in midwinter, with winter lows near 18°F.

Climate normals: NOAA 1991-2020 monthlies, LAMBERTVILLE station (2 mi away), adjusted for elevation.

Geology at Mt. Gilboa

This spot sits on Lockatong Formation, mapped as siltstone mudstone and sandstone mudstone that formed roughly 235 to 200 million years ago. Sedimentary rock like this erodes unevenly, so the most productive collecting is typically along fresh cuts, badland slopes, and active drainages.

Mapped unit

Lockatong Formation

Age

235–200 Ma (Late Triassic)

Rock types

siltstone mudstone and sandstone mudstone

Elevation

220 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.

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.

• New Jersey Geological and Water Survey
• Monmouth County Park System, fossil collecting rules
• Sterling Hill Mining Museum
• Community submissions reviewed against published agency rules