Pennington Mountain: Calcite & Celadonite Rockhounding in Mercer County, New Jersey

Updated June 2026

Pennington Mountain is a mapped rockhounding spot in Mercer County, New Jersey. Reported finds include calcite, celadonite, epidote. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Mercer County
State: New Jersey
Nearest road: Woodsville Road
Postcode: 08525
Coordinates: 40.36165, -74.80631

Geology at Pennington Mountain

This spot sits on Passaic Formation, mapped as siltstone that formed roughly 235 to 175 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: Passaic Formation
Age: 235–175 Ma (Late Triassic to Early Jurassic)
Rock types: siltstone
Elevation: 270 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 Pennington Mountain

Best months: March to November. Typical highs run 86°F in midsummer and 40°F in midwinter, with winter lows near 22°F.

Climate normals: NOAA 1991-2020 monthlies, EWING 3 WNW station (6 mi away).

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.

Sources: RockHoundR public spot dataset, app land overlays, and local agency review before each trip.

Found at Pennington Mountain

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 Pennington Mountain.

Across the state line from Pennington Mountain

Pennington Mountain is close enough to the New Jersey border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Pennington Mountain FAQ

Where is Pennington Mountain?+

Pennington Mountain is in Mercer County, New Jersey, at 40.36165, -74.80631. Nearest road: Woodsville Road.

What rocks and minerals can you find at Pennington Mountain?+

Pennington Mountain is reported to produce Calcite, Celadonite, Epidote.

Is collecting allowed at Pennington Mountain?+

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 Pennington Mountain?+

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 Pennington Mountain?+

The most comfortable months at Pennington Mountain are March to November.

How do I get to Pennington Mountain?+

Open the directions link to navigate to 40.36165, -74.80631 in Google Maps. The nearest road is Woodsville Road.

More rockhounding in New Jersey

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Open Pennington Mountain on the map

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