Union Furnace: Calcite & Fluorite Rockhounding in Huntingdon County, Pennsylvania

Updated June 2026

Union Furnace is a mapped rockhounding spot in Huntingdon County, Pennsylvania. Reported finds include calcite, fluorite. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Huntingdon County
State: Pennsylvania
Nearest road: Limestone Road
Postcode: 16683
Coordinates: 40.62425, -78.16570

Geology at Union Furnace

This spot sits on Coburn Formation through Loysburg Formation, undivided, mapped as limestone, shale, and dolostone that formed roughly 485 to 445 million years ago. Carbonate rock like this is the classic host for lead, zinc, and fluorite mineralization, which typically follows old cavities and replacement zones.

Mapped unit: Coburn Formation through Loysburg Formation, undivided
Age: 485–445 Ma (Ordovician)
Rock types: limestone, shale, and dolostone
Elevation: 850 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 Union Furnace

Best months: March to November. Typical highs run 83°F in midsummer and 35°F in midwinter, with winter lows near 19°F.

Climate normals: NOAA 1991-2020 monthlies, PHILIPSBURG 2 S station (17 mi away), adjusted for elevation.

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 Union Furnace

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 Union Furnace.

Across the state line from Union Furnace

Union Furnace 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.

Union Furnace FAQ

Where is Union Furnace?+

Union Furnace is in Huntingdon County, Pennsylvania, at 40.62425, -78.16570. Nearest road: Limestone Road.

What rocks and minerals can you find at Union Furnace?+

Union Furnace is reported to produce Calcite, Fluorite.

Is collecting allowed at Union Furnace?+

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 Union Furnace?+

A rock hammer, gloves, and safety glasses cover old mining-district ground. Stay out of shafts and adits; the best specimens typically come from dump piles.

When is the best time to visit Union Furnace?+

The most comfortable months at Union Furnace are March to November.

How do I get to Union Furnace?+

Open the directions link to navigate to 40.62425, -78.16570 in Google Maps. The nearest road is Limestone Road.

More rockhounding in Pennsylvania

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Open Union Furnace on the map

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