Tilly Foster Iron Mine: Magnetite & Brucite Rockhounding in Putnam County, New York

Updated June 2026

Tilly Foster Iron Mine is a mapped rockhounding spot in Putnam County, New York. Reported finds include magnetite, brucite, chondrodite, clinochlore, titanite. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Putnam County
State: New York
Nearest road: Old Mine Road
Postcode: 10509
Coordinates: 41.41298, -73.64211

Geology at Tilly Foster Iron Mine

This spot sits on Biotite-quartz-plagioclase gneiss, mapped as biotite gneiss that formed roughly 1600 to 1000 million years ago. Metamorphic rock like this weathers into resistant float, and minerals that survive transport typically concentrate in nearby drainages.

Mapped unit: Biotite-quartz-plagioclase gneiss
Age: 1600–1000 Ma (Mesoproterozoic)
Rock types: biotite gneiss
Elevation: 430 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 Tilly Foster Iron Mine

Best months: April to November. Typical highs run 79°F in midsummer and 34°F in midwinter, with winter lows near 17°F.

Climate normals: NOAA 1991-2020 monthlies, CARMEL 4N station (4 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 Tilly Foster Iron Mine

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 Tilly Foster Iron Mine.

Across the state line from Tilly Foster Iron Mine

Tilly Foster Iron Mine is close enough to the New York border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Tilly Foster Iron Mine FAQ

Where is Tilly Foster Iron Mine?+

Tilly Foster Iron Mine is in Putnam County, New York, at 41.41298, -73.64211. Nearest road: Old Mine Road.

What rocks and minerals can you find at Tilly Foster Iron Mine?+

Tilly Foster Iron Mine is reported to produce Magnetite, Brucite, Chondrodite, Clinochlore, Titanite.

Is collecting allowed at Tilly Foster Iron Mine?+

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 Tilly Foster Iron Mine?+

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 Tilly Foster Iron Mine?+

The most comfortable months at Tilly Foster Iron Mine are April to November.

How do I get to Tilly Foster Iron Mine?+

Open the directions link to navigate to 41.41298, -73.64211 in Google Maps. The nearest road is Old Mine Road.

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Open Tilly Foster Iron Mine on the map

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