No booking required. You stop at the store, buy a pass and a map of the digging area, and drive the short distance to the Herkimer ground with parking a few steps from where you work. Mine hours run nine in the morning until sunset, open daily through mid-October.
The 2026 rates are modest. Non-campers pay sixteen dollars for ages twelve and up and ten for six to eleven, with under-sixes free; if you are staying on the campground it drops to fourteen and eight. Tools are rented rather than assumed: a crack hammer is four dollars, a rock chisel three, a sift box five, a shovel four, a sledgehammer seven. That list is worth reading as a packing hint, because it tells you exactly what people actually use here.
What you are after is a Herkimer diamond, which is not a diamond at all. They are double-terminated quartz crystals, complete at both ends, and the name comes from their clarity and their well-formed faces. Workmen found them in quantity in the late eighteenth century while cutting into Mohawk Valley dolomite, and the crystals are also known as Middleville or Little Falls diamonds after the first sites.
The story in the rock is a slow one. About 500 million years ago a shallow sea took sediment off the ancient Adirondacks to the north, and those carbonates hardened into the Little Falls Formation. Acidic water later dissolved cavities in it while it was buried. The dolomite is Cambrian, but the quartz inside the vugs is interpreted as Carboniferous, grown very slowly as burial warmed the rock, which is precisely why the crystals are so clear. Look inside one and you may find salt water or petroleum trapped in it, carbon dioxide, or a fleck of black hydrocarbon, which is the commonest solid inclusion of all.
Crystal Grove is known for crystals on matrix and for druzy.
Herkimer “diamond”
Other places on the map within a couple of hours.
