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Cornwall: Actinolite & Andradite Rockhounding in Lebanon County, Pennsylvania

Public accessBest spot13 mineralsLebanon County, PennsylvaniaUpdated July 2026
Minerals reported
13
Elevation
1,050 ft
Best months
March to November

Cornwall is one of the most famous iron deposits in eastern North America, a magnetite skarn worked for over two centuries. The contact-metamorphic assemblage produced a rich suite of andradite garnet, actinolite, calcite, chlorite, diopside, epidote and magnetite that is textbook Pennsylvania mineralogy. Its historical and mineralogical significance makes it a marquee locality. Reported finds include actinolite, andradite, calcite, chlorite, diopside, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Plan your visit

Generally open to casual rockhounding

Nearest road
Twenty-Eighth Division Highway
Postcode
17016
Get directionsView on Google Maps

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.

Access note: The historic Cornwall mine itself is reclaimed and much of it is private, so collecting is limited to tailings, dumps and roadcuts around the district. Get landowner permission before entering any posted ground and verify current access before you go.

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 Cornwall

Comfortable months (45 to 90°F highs)

Best months: March to November. Typical highs run 82°F in midsummer and 35°F in midwinter, with winter lows near 20°F.

Climate normals: NOAA 1991-2020 monthlies, LEBANON 2 W station (7 mi away), adjusted for elevation.

Geology at Cornwall

This spot sits on Hammer Creek Formation, mapped as sandstone that formed roughly 250 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
Hammer Creek Formation
Age
250–200 Ma (Triassic)
Rock types
sandstone
Elevation
1,050 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.

Today's weather

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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.

Found at Cornwall

Each name 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 Cornwall.

Across the state line from Cornwall

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

Cornwall FAQ

Where is Cornwall?+
Cornwall is in Lebanon County, Pennsylvania, at 40.25479, -76.39783. Nearest road: Twenty-Eighth Division Highway.
What rocks and minerals can you find at Cornwall?+
Cornwall is reported to produce Actinolite, Andradite, Calcite, Chlorite, Diopside, Epidote, Fluorite, Grossularite Garnet, Labradorite, Magnetite, Moonstone, Prehnite, Pyrite.
Is collecting allowed at Cornwall?+
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 Cornwall?+
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 Cornwall?+
The most comfortable months at Cornwall are March to November.
How do I get to Cornwall?+
Open the directions link to navigate to 40.25479, -76.39783 in Google Maps. The nearest road is Twenty-Eighth Division Highway.

More rockhounding in Pennsylvania

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