My recent finds while hiking in Upstate New York. I a really nice clear small crystal and a small crystal chunk. Not bad for a Saturday hike.
Answer: You can find Herkimer Diamonds in the Little Falls Dolostone formation in Upstate NY. More Specifically they very prevalent in the Middleville NY area. There are two public operating mines that are open to the general public. Ace of Diamond Mines and Herkimer Diamond Mines both located in Middleville. Herkimer Diamond