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

Permission requiredBest spot1 mineralHerkimer County, New YorkUpdated August 2026

Mineral reported: 1
Elevation: 610 ft
Best months: April to November

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.

Plan your visit

Permission required before collecting

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

Get directions View on Google Maps

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

Land & collecting status

Permission required before collecting

Requires landowner or agency permission before any collecting. Do not enter without explicit authorization.

Access note: Closed to the public since 2024 and expected to remain closed through the 2026 season while ownership is disputed in court. Do not travel here without confirming directly that it has reopened.

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.

Best time to visit Ace of Diamonds & Herkimer Diamond Mine

31°J

33°F

41°M

55°A

69°M

77°J

82°J

80°A

74°S

60°O

48°N

36°D

Comfortable months (45 to 90°F highs)

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.

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.

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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.

New York State Museum, Geological Survey
NYS DEC land use rules
Herkimer Diamond Mines
Community submissions reviewed against published agency rules

Found at Ace of Diamonds & Herkimer Diamond Mine

Each name 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.

Herkimer Diamond MinesHerkimer County, New York · 0 mi away
General Area (Herkimer County 2)Herkimer County, New York · 1 mi awayHerkimer Diamond
General Area (Herkimer County 1)Herkimer County, New York · 2 mi awayHerkimer Diamond
General Area (Herkimer County 3)Herkimer County, New York · 2 mi awayHerkimer Diamond
Treasure Mountain MineHerkimer County, New York · 7 mi awayQuartz, Fluorite, Calcite
Ace of Diamonds MineHerkimer County, New York · 8 mi awayHerkimer Diamond
Hidden Gem MineHerkimer County, New York · 8 mi awayHerkimer Diamond
Diamond Mountain MiningHerkimer County, New York · 10 mi awayGarnet, Epidote, Quartz

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?+

Permission required before collecting. Requires landowner or agency permission before any collecting. Do not enter without explicit authorization. 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.

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