Northfield Mountain: Garnet Rockhounding in Franklin County, Massachusetts

Quick details

Access

Public area

County

Franklin County

State

Massachusetts

Nearest road

Four Mile Brook Road

Postcode

01360

Coordinates

42.62611, -72.43721

Geology at Northfield Mountain

This spot sits on Dry Hill Gneiss, mapped as gneiss that formed roughly 635 to 540 million years ago. Metamorphic rock like this is where garnet, staurolite, and kyanite typically grow as the rock recrystallizes under heat and pressure.

Mapped unit

Dry Hill Gneiss

Age

635–540 Ma (Neoproterozoic)

Rock types

gneiss

Elevation

1,030 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 Northfield Mountain

Best months: April to November. Typical highs run 82°F in midsummer and 32°F in midwinter, with winter lows near 12°F.

Climate normals: NOAA 1991-2020 monthlies, ORANGE MUNI AP station (9 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 Northfield Mountain

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

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