Washington Crossing State Park: Black Jasper Rockhounding in Mercer County, New Jersey

Updated June 2026

Washington Crossing State Park is a mapped rockhounding spot in Mercer County, New Jersey. Reported finds include black jasper. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Permission required
County: Mercer County
State: New Jersey
Nearest road: Blue Dot Trail
Postcode: 08560
Coordinates: 40.30935, -74.86421

Geology at Washington Crossing State Park

This spot sits on Passaic Formation, mapped as siltstone that formed roughly 235 to 175 million years ago. Tough silica like agate, jasper, and chert typically weathers out of beds like these and collects as float in drainages and on deflation surfaces.

Mapped unit: Passaic Formation
Age: 235–175 Ma (Late Triassic to Early Jurassic)
Rock types: siltstone
Elevation: 200 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 Washington Crossing State Park

Best months: March to November. Typical highs run 86°F in midsummer and 40°F in midwinter, with winter lows near 23°F.

Climate normals: NOAA 1991-2020 monthlies, EWING 3 WNW station (2 mi away).

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.

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

Found at Washington Crossing State Park

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

Black Jasper Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Washington Crossing State Park.

Across the state line from Washington Crossing State Park

Washington Crossing State Park 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.

Washington Crossing State Park FAQ

Where is Washington Crossing State Park?+

Washington Crossing State Park is in Mercer County, New Jersey, at 40.30935, -74.86421. Nearest road: Blue Dot Trail.

What rocks and minerals can you find at Washington Crossing State Park?+

Washington Crossing State Park is reported to produce Black Jasper.

Is collecting allowed at Washington Crossing State Park?+

Permission required before collecting. Requires landowner or agency permission before any collecting. Do not enter without explicit authorization. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Washington Crossing State Park?+

Most agate and jasper is surface float: bring a spray bottle, a pick or small shovel, and a sturdy bag. Wet stones show their banding and translucence.

When is the best time to visit Washington Crossing State Park?+

The most comfortable months at Washington Crossing State Park are March to November.

How do I get to Washington Crossing State Park?+

Open the directions link to navigate to 40.30935, -74.86421 in Google Maps. The nearest road is Blue Dot Trail.

More rockhounding in New Jersey

See all 72 New Jersey spots →

Open Washington Crossing State Park on the map

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