In the hills between the great Adirondack Park and the historic Mohawk River valley lies an ancient deposit of marine sediment that holds one of nature’s most beautiful creations, the world’s only naturally occurring “cut” gemstone: the Herkimer Diamond. Herkimers are actually double-terminated Quartz crystals of unusual brilliance and clarity. These traits and their shape led to their originally being called “Diamonds,” and the name stuck even after science proved their actual composition. As for their origin, Herkimers were most likely formed by precipitation from solutions percolating down through the extremely hard early Ordovician rock from which they are now mined. Tests conducted on enhydro specimens with air bubbles concluded that Herkimers were formed at low temperatures, probably less than 200 degrees Fahrenheit.
The HDC and Ace-of-Diamonds mines are actually located in the town of Middleville, not Herkimer. If you are lucky enough to be there on a day when the regulars are around, do not hesitate to ask questions. There are folks who come here all the time, and even limit their field collecting (all of it) to one particular mine. They are also some of the nicest rockhounds you’ll ever meet.
On the day that we were there, we were shown the ropes by Larry Dubois, who is mentioned on page 44 of the book. “The Book?”, you might ask. Yes, there is a book by Barry Moore named HERKIMER DIAMONDS: A COMPLETE GUIDE FOR THE PROSPECTOR AND COLLECTOR that you can order from Lapidary Journal (publication #B0266). It tells all about the Herkimer Development Corp. mines and their “Diamonds.” If you decide to make the trip, get the book, read it, and believe it. Unless you are planning a major assault with power tools, this is the place to go.
Since it had rained during the night, my wife and I started our day at opening time (9 am sharp) by picking up loose diamonds off of the surface. We were some of the first ones to enter the mine, so we did pretty well – picking up a dozen or so each in half an hour. Once we had covered the quarry we started breaking rocks that looked promising and found several nice matrix specimens. About this time, a young couple with three small boys in tow came in and started looking on the surface. I was initially embarrassed for having picked the quarry over first, but eventually I become totally embarrassed when I realized by the boy’s excited cries of discovery that they were doing better than we did. Ah, for a sharp eye just a wee bit closer to the ground.
When Larry started cleaning up his work area from the day before, he threw back some rocks he didn’t plan on breaking. I asked him if he wanted the, and upon his generous OK to help myself, I proceeded to carry the more promising ones a few yards away and started breaking them with my twelve pound sledge-hammer. At Herkimer, this is the largest hammer you can use in the mine and there are no power tools or machinery allowed. I really don’t see why anyone would want to swing anything heavier than twelve pounds all day; but if I actually meet someone who could, I certainly would not be the first one volunteering to deny them the pleasure.
The rock at Herkimer is extremely hard and does not break easily. Using only hand tools, you expect to become worn out in a hurry, so the tools you use are of great importance. It has been a long time since I’ve heard steel referred to with the reverence and respect a well tempered piece of metal deserves. Here at Herkimer, the regulars are very fond of their steel – some even recommend talking to it. The sound of a finely sharpened leaf spring singing tight in a crack is music to their ears. Often they will drive home several leaf springs and a wedge or two and leave them overnight. Larry’s buddy greeted him that morning by observing, “See you already got your steel working.” Indeed, it was still tight from the day before.
Larry drove in one more thin leaf spring and went to work on a previously loosened section of “ledge.” Once it was broken out, he raised it with wood wedges and barred it away from the wall. When he was sure that the loosened boulder was secure, he reached into the water that had pooled under it and came out with a handful of diamonds. Larry had hit a nice pocket, but the rest was yet to come. I came over to help him move the boulder. It was too heavy, so we split it. As I held one of the halves away, Larry rolled the other one pocket side up exposing a beautiful diamond measuring almost 2 x 3 x ¾ inches with a little ½ x ¾ diamond perched at an angle on one end. It looked like a little turtle with its head sticking out, so aptly dubbed “Mr. Turtle”, it was carefully wrapped to become part of Larry’s personal collection.
For some reason, I lost interest in cracking rocks and decided to break out the heavy metal and start working on my own section of ledge. One thing I did not have with me was a hoe. A hoe with a sawed-off handle was just the ticket to clean all of the loose dirt and rock away from the wall. I looked around and spotted an area that had two existing cracks in it, one vertical and one parallel to the face of the wall. This was lucky because you usually have to start your own cracks around here. After cleaning up a small area with a borrowed hoe, I proceeded to set a chisel between the floor of the quarry and the two-foot-tall face of ledge that I was working on. I set another chisel on the opposite side of the vertical crack and chiseled out a starting place for my leaf springs. The leaf springs that I used were from the rear of a 1967 Chevrolet pickup truck. After opening a horizonal crack along the bottom of the face, I broke the rock out with two wooden wedges. This was two hours of hard work swinging a sledge-hammer – but the rewards were worth it.
The first piece of rock that I barred loose and flipped over had a pocket with double diamonds surrounded by pretty Calcite rhombi. Underneath where it had lain were several more pockets with diamonds in them. My wife and I spent the next hour or two totally involved with barring out rock and exposing the pockets that it contained. Each piece that came out revealed a new pocket with more beautiful diamonds. It was fantastic! I even caught my wife using a hammer can chisel on the smaller pieces while I was busy breaking up a big one. Folks, it doesn’t get any better than this: One diamond after another sparkling in the sunshine for the first time in 500 million years. What a thrill!
We realized how tired we were after working all of the rock that I had broken loose and decided to call it a day. We picked up a couple of hot dogs and cold drinks at the little lunch stand at the mine entrance and cleaned up in the large restrooms (plenty of room to change clothes here.) Then we toured the mineral museum that is above the rock shop. They have a very nice display of a reconstructed pocket, as well as plenty of other spectacular specimens. We picked up your “must have” souvenir Herkimer diamond pouch and with one last fond look toward the mine, headed back south to Herkimer. As we headed back out on the thruway to New Jersey, the sun burst back through the clouds and a huge rainbow appeared over the tranquil Mohawk river valley. As my mind wandered to the proverbial pot of gold, my eyes traced its downward arc to the northwest where it disappeared behind a hill. Where did it end? Middleville, my friends, Middleville.
TIPS FOR THE TRIP
If you decide to camp out, the mine has a KOA campground right across the street. While it is expensive, it is as nice as it is convenient and has a stream with tubing available right next to it. They also have cabins, but you need your own linens, etc, so we stayed at the Herkimer Hotel, which has a pool, nice rooms and is right on the thruway. It is about one thousand miles from Atlanta to the mine. Breathers for the kids along the way include Luray (and many other) caverns, Natural Bridge, the Hershey Chocolate Factory and an amusement park near Harrisburg, PA and the National Baseball Hall of Fame in Cooperstown, NY. Once in Herkimer, be sure to see the Remington Gun Museum just outside of town. The mine is open from April 1 through December 1, weather permitting. For more information call 315-891-7355.
NOTE
There are two other diamond mines besides the HDC and Ace of Diamonds. I was given a lot of advice on which one of the four to visit – most of it contradictory. I decided to check out them all. We did not have time to visit Ace of Diamonds, but as it is located right next to the HDC mine, I would presume that the digging and diamonds would be quite similar. We spent half a day at “Fonda.” For one dollar a day per person, you can go in with anything short of a bulldozer. However, there are NO facilities and the layer with the pockets runs from eight to ten feet deep. Most of the holes dug down to this layer are claimed and roped off. If you have plenty of time, a generator, a rotary hammer drill and plenty of help to move several tons of dirt and rock, you can hit a pocket there that will hold some very large diamonds. The largest diamond found at Fonda was the size of a football and was rumored to weigh in at 22 pounds. During our visit, we collected from the surface and broke a few rocks and found several nice diamonds and matrix specimens for our efforts. It was well worth the price of admission.
We spent the second half of our day at Crystal Grove in St. Johnsville. It had just rained so when we went into the mine and found that we were the only ones there, we figured to do some real looking on the surface. Wrong! There was not one decent diamond to be found. The stuff in the rock shop was not all that great either. Oh well, maybe that was why we were the only ones there. I would definitely pass on this one, folks.
To get to the Fonda mine, also known as Hastings or Diamond Acres, take exit 28 off the thruway (Rt. 90) and go north across the river to Route 5. Take a left on Route 5 (west) and look for a coal yard on your left. Hickory Hill Road will fork off to your right up a hill. Take this to Martin road which is also marked with an intersection sign and turn right. Stone Arabia Road should be your next left. After you cross the intersection of England Road, there will be a white building on the right. Start looking for a small break in the bushes on your left, this is the driveway to the mine. You will see a trailer to the right with an open field beyond it.
Editor’s Note: You can find updated information about the Herkimer Diamonds at the following web site: https://www.herkimerdiamond.com/, https://www.herkimerdiamond.com/herkimer-diamond-mines/, https://geology.com/articles/herkimer-diamonds.shtml, https://www.roadsideamerica.com/story/6164
Herkimer Diamond Mines
Address: 4626 Route 28 North, Middleville, NY
Directions: I-90 exit 30, about nine miles north on Rte 28, on the west side.
Hours: daily 9 am – 5 pm, Apr 15-Oct 31. (Call to verify)
Phone: 315-891-7355