Quick answer: finding a Herkimer diamond is easy. Several pay-to-dig mines in Herkimer and Montgomery counties, New York, let visitors pick small loose crystals out of rubble for a modest fee, and children routinely find them. Finding a large, clear crystal is hard: it means breaking into very tough dolostone with sledgehammers and wedges to open an intact pocket, and many pockets are empty.
Where the crystals actually are
Herkimer diamonds grew inside cavities (vugs) in a single rock unit, the Cambrian-age Little Falls Dolostone, about 500 million years old. Geology.com describes the cavities as ranging from smaller than a pea to several feet across, often lined with drusy quartz and coated in a tarry hydrocarbon. A cavity can hold anywhere from a few crystals to a few thousand. (The rock layer itself is covered in depth in The Mohawk Valley: The Specific Rock Layer Behind New York’s Herkimer Diamonds.)
Rock & Gem’s first-hand account of digging adds the practical picture. After clearing forest soil, you dig through several feet of shattered glacial rock, where loose crystals can turn up. Below that sits the “pocket layer”: solid dolostone from several inches to over two feet thick. Pockets were roughly oval with a central rise where crystals were usually attached, averaging about two and a half feet across. In one stretch they ran in a chain only four to six inches apart; elsewhere, about one every two feet.
Three ways people dig
- Scavenging: walking the rubble and quarry floor for crystals already weathered or knocked loose. Geology.com calls this the safest method and the best one for kids.
- Find and break: choosing rocks with visible vugs on the outside and splitting them with a heavy hammer. Most are empty; some open onto crystals.
- Cavity mining: using sledgehammers and wedges along existing fractures to open large pockets in the bedrock. This is where the big crystals come from, and it is hard physical work. Geology.com notes power equipment is not permitted at the public fee-dig mines.
Why it is harder than it sounds
- The rock fights back. Dolostone here is very tough and often heavily silicified. Rock & Gem describes it as very hard, especially where it has few fractures.
- Pockets disappoint. Some are barren. Some are full of large but internally fractured crystals. Others are packed with black hydrocarbon granules and hundreds of small bright crystals. Two pockets the Rock & Gem author opened at Ace of Diamonds were nearly half full of wet clay that had to be screened.
- Water. Seepage is common enough that the author recommends keeping a gas pump on site.
- Injury. Crystal shards cut; chisels break. Safety glasses, gloves, and long pants are standard advice from both sources.
- Weather. Winter digging is possible in mild years, but a severe winter (2015) stopped mining entirely at the site Rock & Gem described.
Where you can legally dig
Nearly all of the ground is private, so access means a fee or a claim. The established operations named by Geology.com and Rock & Gem include Ace of Diamonds Mine, Herkimer Diamond Mines, and Crystal Grove Diamond Mine & Campground near St. Johnsville, plus guided or claim-based digging at sites like Hastings Farm, where claims run about 20 by 40 feet and are limited in number. Several rent or sell tools on site.
A short history of finding them
People were finding these crystals long before fee mines existed. Geology.com notes that the Mohawk people and early settlers knew of them, used them as amulets and tools, and traded them; interest dropped when European glass beads arrived in the early 1600s. Today the crystals you see in shops, including our Herkimer Diamond Quartz Cluster — Herkimer Mountain, New York (collected in 2023) and Herkimer Quartz Druzy Cluster — New York, still come out of the ground the same way: by hand, one pocket at a time.
Quick FAQ
Can kids find Herkimer diamonds?
Yes. Scavenging loose crystals from the rubble at a fee-dig mine is the easiest method and is commonly recommended for children.
What tools do I need to dig Herkimer diamonds?
A crack hammer or sledgehammer, chisels and wedges, safety glasses, gloves, and long pants. Several mines rent tools on site.
Where do the biggest Herkimer diamonds come from?
From intact cavities opened in the solid dolostone pocket layer, which takes heavy hand tools (or heavy equipment at commercial quarries) and patience.
Sources
- Geology.com: Herkimer Diamonds — Doubly Terminated Quartz Crystals
- Rock & Gem Magazine: Herkimer Diamonds in Spades
Related pieces in the shop
- Herkimer Diamond Quartz Cluster — Herkimer Mountain, New York
- Herkimer Quartz Druzy Cluster — New York
- Large Double-Terminated Herkimer Diamond Quartz — Fort Plain, New York
- Herkimer Diamond Quartz Crystal — Fort Plain, New York
- Herkimer Diamond Quartz Cluster on Matrix — Mohawk Valley, New York
- Various Quartz Specimens Lot (Herkimer, Points & Chunks)
