Best spot

Ace of Diamonds & Herkimer Diamond Mine: Herkimer Diamond Rockhounding in Herkimer County, New York

Updated July 2026

The Ace of Diamonds and neighboring Herkimer Diamond Mine sit on the Cambrian Little Falls Dolostone, the type ground for the doubly-terminated clear quartz crystals known worldwide as Herkimer diamonds. It is the single most famous rockhounding destination in New York, with productive vug-lined dolostone that reliably yields loose, water-clear crystals. Reported finds include herkimer diamond. Below: coordinates, access notes, nearby spots, and trip-planning links.

Ace of Diamonds & Herkimer Diamond Mine photos

Public image records connected to this spot or its reported material.

1 photo

Herkimer diamond, a doubly terminated quartz crystal from the Herkimer district, New York

Quick details

Access: Public area
County: Herkimer County
State: New York
Postcode: 13406
Coordinates: 43.13146, -74.97414

Geology at Ace of Diamonds & Herkimer Diamond Mine

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 Ace of Diamonds & Herkimer Diamond Mine

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

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 Ace of Diamonds & Herkimer Diamond Mine

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

Herkimer Diamond Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Ace of Diamonds & Herkimer Diamond Mine.

Ace of Diamonds & Herkimer Diamond Mine FAQ

Where is Ace of Diamonds & Herkimer Diamond Mine?+

Ace of Diamonds & Herkimer Diamond Mine is in Herkimer County, New York, at 43.13146, -74.97414.

What rocks and minerals can you find at Ace of Diamonds & Herkimer Diamond Mine?+

Ace of Diamonds & Herkimer Diamond Mine is reported to produce Herkimer Diamond.

Is collecting allowed at Ace of Diamonds & Herkimer Diamond 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 Ace of Diamonds & Herkimer Diamond 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 Ace of Diamonds & Herkimer Diamond Mine?+

The most comfortable months at Ace of Diamonds & Herkimer Diamond Mine are April to November.

How do I get to Ace of Diamonds & Herkimer Diamond Mine?+

Open the directions link to navigate to 43.13146, -74.97414 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in New York

See all 74 New York spots →

Open Ace of Diamonds & Herkimer Diamond Mine on the map

Use the RockHoundR app for live land overlays, weather, geology, directions, and saved finds.