About this location
Ace of Diamonds Mine & Campground is a family-run pay-to-dig site at 84 Herkimer Street in Middleville, New York, in the heart of Herkimer County's famous Herkimer diamond country — the double-terminated quartz crystals prized for their clarity that formed in dolomite vugs here over roughly 500 million years.[^1][^2] As of mid-2026, the mine, campground, and gift shop are closed for the entire season due to an ongoing court case, with reopening uncertain.[^3] Note the site is a distinct business from the larger "Herkimer Diamond Mines" attraction near the village of Herkimer — the database name combines both, but the coordinates given match Ace of Diamonds in Middleville specifically, so that's what this dossier covers. Check current status directly before planning any trip.
Always seek permission where required, follow local laws, and practice Leave No Trace. Locations and details are community-submitted and may be inaccurate. Not sure what's legal here? Read our full guide to rockhounding laws by land type.
Found Here
- Herkimer Diamond — double-terminated quartz crystals of exceptional clarity, native to dolomite outcrops in the Middleville/Herkimer County area, historically also called Middleville diamonds or Little Falls diamonds.[^1][^2]
Difficulty
Getting there
84 Herkimer Street, Middleville, NY 13406.[^3] Middleville sits in Herkimer County in the Mohawk River Valley region of central New York.
Collecting here
Historically (when open), digging is done with hand tools in the mine's exposed dolomite/vug material, with tool rental available on-site for those without their own.[^4] Not applicable while the site remains closed.
Rates and hours
UNVERIFIED — site is closed for the entire 2026 season. Historical rates reported in reviews and listings prior to closure: sources conflict, with one listing adults at $8.50 and children (4–7) at $4, and another describing $13 per day with $1 tool rental — these figures were not confirmed against the operator's own current pricing and should not be relied on. Historical season was reported as April through October, daily 9am–5pm.[^4] Contact: (315) 891-3855 / [email protected].[^3] Verified against search results, July–August 2026.
Know before you go
This is private property and the business is currently closed for the 2026 season due to an ongoing court case, with no confirmed reopening date.[^3] Do not attempt to visit or dig without confirming the site has reopened — call ahead. If planning a Herkimer diamond trip in the area, note there are other operating pay-to-dig sites nearby in Herkimer County; confirm which specific business is open before traveling.
Location on Map
Coordinates: 43.13146, -74.97414
Nearby rockhounding locations
- Herkimer Diamond MinesNY · 0.2 mi
- General Area (Herkimer County 1) — Herkimer DiamondNY · 1.5 mi
- General Area (Herkimer County 2) — Herkimer DiamondNY · 1.4 mi
- General Area (Herkimer County 3) — Herkimer DiamondNY · 1.7 mi
- Treasure Mountain Mine — Quartz, FluoriteNY · 7.4 mi
- Herkimer Diamond Mines (general)NY · 7.7 mi
More Herkimer Diamond locations in New York
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- 3124B, Leptaena-Megakozlowskiella community, Onondaga Limestone, NY — FossilNY
- 3135, Atrypa-Coelospira-Nucleospira community, Onondaga Limestone, NY — FossilNY
Frequently asked questions
Is Ace of Diamonds Mine in Middleville, NY open?
No — as of mid-2026, the mine, campground, and gift shop are closed for the entire season due to an ongoing court case. Call (315) 891-3855 to check current status before visiting.
What is a Herkimer diamond?
A Herkimer diamond is a double-terminated quartz crystal, prized for its clarity, native to dolomite outcrops in New York's Herkimer County and Mohawk River Valley — not an actual diamond despite the name.
Is Ace of Diamonds Mine the same as Herkimer Diamond Mines?
No — they are two separate, similarly-named businesses in the same general area. Ace of Diamonds Mine & Campground is in Middleville; Herkimer Diamond Mines is a separate, larger attraction near Herkimer village. Confirm which one you're planning to visit.
Where is Ace of Diamonds Mine located?
84 Herkimer Street, Middleville, NY 13406, in Herkimer County.
⚠️ Always verify current regulations, weather conditions, and access requirements before visiting any location. Information provided is based on community submissions and may not be current or accurate.
Sources
- Wikipedia, "Herkimer diamond" — definition, formation process, alternate names (Middleville/Little Falls diamonds).
- Show Mines of the United States of America, Ace of Diamonds Mine entry — https://www.showcaves.com/english/usa/mines/AceOfDiamonds.html — general site description (referenced via search; not independently fetched).
- herkimerdiamonds.com (Ace of Diamonds Mine & Campground official site) — https://herkimerdiamonds.com/ — confirms 2026 season closure due to ongoing court case, address, and phone number, per search-result summary of the site's current content.
- Aggregated review/listing sources (Yelp, RoverPass, iloveny.com) — historical hours (April–October, 9am–5pm) and conflicting rate figures; treated as lower-confidence since figures conflict between sources and predate the current closure.
Recommended Gear for New York
Estwing E3-22P Rock Pick
The industry-standard 22oz geological hammer. One-piece forged steel with shock-reduction grip.
Clear Anti-Fog Safety Glasses (4 Pack)
Adjustable, anti-fog lenses for clear vision in any conditions. About $5 per pair.
Watertight Medical Kit
Compact, waterproof first aid kit with bandages, moleskin, and field essentials.
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