Herkimer Diamond Mines: Rockhounding in Herkimer County, New York

Quick details

Access

Paid / fee dig

County

Herkimer County

State

New York

Postcode

13406

Coordinates

43.12919, -74.97635

Geology at Herkimer Diamond Mines

This spot sits on Beekmantown Group, mapped as dolostone that formed roughly 495 to 470 million years ago. Carbonate rock like this dissolves and weathers readily, so fresh road cuts, quarries, and creek exposures are typically the most productive ground.

Mapped unit

Beekmantown Group

Age

495–470 Ma (Furongian to Early Ordovician)

Rock types

dolostone

Elevation

610 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 Herkimer Diamond Mines

Best months: April to November. Typical highs run 82°F in midsummer and 31°F in midwinter, with winter lows near 12°F.

Climate normals: NOAA 1991-2020 monthlies, LITTLE FALLS CITY RSCH station (7 mi away), adjusted for elevation.

Land & collecting status

Pay-to-dig site

This is a fee-dig location. Hours, prices, and what you can keep vary by operator. Call ahead before driving out.

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.