Ace of Diamonds Mine

Useful Information

Location: 84 Herkimer Street, Middleville, NY 13406.
(43.132631, -74.973267)
Open: APR to OCT daily 9-17.
Fee: Adults USD 14, Children (4-7) USD 7, Children (0-3) free.
Classification: MineFee Mining MineSchmucksteine
Light: n/a
Guided tours: self guided
Photography: allowed
Accessibility: no
Address: Ace of Diamonds Mine, 84 Herkimer Street, Middleville, NY 13406, Tel: +1-315-891-3855.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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The Herkimer Diamonds are found in dolomite limestone. It was down lifted and under high pressure and temperature quartz rich water deposited the quartz very slowly in pockets or cavities. As the dolomite is rather easily dissolved by rain water which contains carbon dioxide, but quartz not, the small crystals are actually freed from the surrounding rocks by weathering. They can be easily found in the soil.


Ace of Diamonds Mine is a open cast or quarry where you can collect Herkimer Diamonds. Those are not diamonds, they are water clear quartz crystals of a hexagonal structure and doubly terminated. That's quite rare, and they actually look a little like small diamonds, hence the name. The deposit at Herkimer is unique and rather small, but it is big enough for two competitors, and so the Ace of Diamond mine and the Herkimer Diamond Mine are only 500 m apart. And as this is America, home of free enterprise, they have a little war going on. As far as we can see Ace of Diamonds Mine is in the lead.

The quartz crystal bearing dolomite reaches the surface near the town Middleville, New York. Weathering and erosion by glaciers has exposed the rock. The area is called Herkimer County, named after the Revolutionary War General Nicholas Herkimer. The crystals were simply named after their location.

This is not a show mine, it is a fee mine where you can collect quartz crystals in an open cast. It seems the residual clays were already removed, so you have to search for mineral geodess in the rock. For the mineral collecting you should wear appropriate clothes. Sturdy shoes, safety eye wear, gloves, and a hat are a good start. Bring equipment like chisels, screens, small shovels, buckets, and hammers. However, be very careful with steel hammers, they might break and the piece of steel will fly away with high speed and may hit and injure someone. Bring a geologist hammer if you have or at least a claw hammer or carpenter hammer, which is made of iron, not of steel. It makes hammering not only safer but also more effective.