Mohawk Valley Mineral Mining by Bill Stephens, PG
Synopsis by Andy Thompson, MSDC Secretary
FROM CAMPAIGN MONITOR:
Having given two earlier presentations to MSDC in the last several years, Bill Stephen's talk updated his audience on the work he has recently completed at the Mohawk Valley Mineral Mine. More broadly, he described in his presentation the unique geology of the Mohawk Valley Mineral District and its many mines, claims, dig sites, and minerals discovered there. --//
Readers: The purpose of this report is to provide readers with highlights from Bill’s presentation as encouragement for readers to visit MSDC’s YouTube channel and view his presentation in its entirety. You can find Bill’s 59-minute talk HERE. Also, as noted in the slide above, Bill has copyrighted this material and granted MSDC permission to post it on our YouTube video channel and report on it in our Mineral Minutes newsletter.
Bill Stephens, well known in mineral and geological circles, is the long-time owner of an environmental consulting company, a professional geologist, president of multiple mineral clubs, and a mineral collector since childhood.
Having given two earlier presentations to MSDC in the last several years, tonight’s talk updated his audience on the work he has recently completed at the Mohawk Valley Mineral Mine. More broadly, he described in his presentation the unique geology of the Mohawk Valley Mineral District outlined in the map below, and its many mines, claims, dig sites, and minerals discovered there.
The entire area has been known for well over a century as a locale for finding beautiful quartz crystals named Herkimer diamonds. Bill described the whereabouts and characteristics of about half a dozen mines in this district. The Mohawk Valley Mineral Mining Inc site is shown above as located at the southern-most point near interstate 90 at the bottom and toward the right of the district outlined in red.
He noted that people call it a “mine” but technically, under New York State law, it is not a mine but rather a club. The MVMM is only two or three years old and has yielded the largest Herkimer crystals on record. Members pay to join the club and then an additional amount for per diem digging privileges.
An Interest that Began in College
Bill shared that he began his own personal mineral field collecting as an undergraduate geology student at the University of Pittsburg. The 1982 photo below documented that beginning. He noted he is the “cool” fellow wearing the Coors Hat.
Here’s the short version of that event which occurred at the mine pictured above as he was headed to a six-week field camp required of all students majoring in geology. While traveling to the field camp, Bill and two classmates noticed, from a distance, a solo rockhound digging into the wall’s crevices at the mine. Bill studied his method of excavating. When that man abandoned the site, Bill took over and continued digging in a wedge area that intersected with joints. He hit upon an elbow-deep pocket that yielded a bonanza of clay-encrusted Herkimers, a few of which are shown below, minus their mud.
The crystals were abundant and he shared the hoard with his two non-collecting classmates. “Pretty well for a first trip” he noted and added that he was never again as successful as he was that first day in the summer of 1982, until decades later when he started using industrial sized excavation equipment.
In his talk to MSDC, Bill was not promoting the mining or collecting in any particular site. But he did observe that for families with little kids, KOA sites seem well suited, one of which is shown on the map below in the top left corner. He said KOA sites typically are all set up to help families. (Interested readers can listen to Bill’s description about 8 minutes into his talk.)
Bill said that today, as a geologist, he has a vested interest in understanding the geological setting of the crystals, pegmatites, and minerals that we love to collect.
“I try to give everyone who listens to my talks just enough geologic and mineralogic information about the specific sites to help them find something rather than wondering around aimlessly and trying to figure out where to start looking.”
He also concisely explained the chemical evolution of the original mineral deposit of the shallow sea minerals which became the Herkimer-rich regions shown in the four red-circled areas in the map below.
Geologic Context
Bill described the “Geologic Context” of the Mohawk Valley Mining region as originating in the late or upper Cambrian, about 485 million years ago. He identified the main rocks in this region where collectors have been finding Herkimer diamonds as being Little Falls Dolostone (LFD), “a rock which contains the mineral dolomite.” As noted in the slide below, the last bullet point, partially obscured, notes that only 6 percent of the New York State Montgomery County area has been found to have the sought-for LFD outcrops. So that is where Herkimer collectors would do well to focus.
The big picture is that the LFD deposits of the Hudson Valley rest atop the Grenville basement rock which is a billion years older than the LFD.
Bill provided additional descriptions of seven “Geologic units” in Montgomery County, NY, and showed his audience maps of the relevant fault lines and the stratigraphy noting the thickness of the layers.
The above “Geologic Context-Facies” illustration shows the Precambrian layer at the bottom, Tribes Hill on top, and in the middle, “Unit B where everyone is getting most of their vugs out.” Bill pointed out that some of the research has been very detailed in generating the many layers, formations, and their depths. But without that data being matched with GPS coordinates, its value is much diminished and areas with high concentrations of vugs cannot be traced across the landscapes.
The fact that Unit B has the wedges where the vugs are located is reminiscent of where Bill, on his 1982 initial trip, discovered his first trove of mud-encrusted Herkimers in an elbow-deep vug. He noted that the Herkimer diamonds are formed in vugs where high temperatures helped transform the early marine deposits of calcium magnesium carbonate and silica into much harder Herkimer quartz crystals.
Table One, below, identifies 12 minerals that frequently have been found in the dolostone rock. Bill talked about each mineral and his own experience finding many of them. He also referred to researcher John Warren who spelled out the three main mineral products that form from the chemical reactions taking place in the vugs and in the area, in general, as the hydrothermal processes, along with the high concentration of salt, invaded the carbonate host rock.
Bill summarized this process: “The salt helped with the silicification and dolomitization which changes limestone into dolomite. What they are not saying here is the Little Falls Dolostone is up to 60 percent silica. It has a lot of quartz in it and that’s why it is so really hard. So it is only along fractures, solutions and pathways that the material evolved and today we can exploit that and get access to the pockets” (about 23 minutes into Bill’s talk).
Specific Aspects of the Mohawk Valley Mineral Mining Area
Having provided considerable information about the geologic context and chemical processes at work in the three-county wide NY area, Bill then gave specifics regarding the MVMM club features including that collecting there it is not inexpensive. Pictured below, to the best of Bill’s knowledge, is the first Herkimer, a seven-pound beauty, reported discovered in the “Monster Pocket.”
In the first several months of MVMM’s operation, collectors were even finding some Herkimers near the surface as they randomly scratched the soil. The cluster pictured below, for example, weighing 12 pounds, was found within the first six months and was discovered close to the surface.
But Bill’s purpose in working there was to provide the owner with engineering recommendations which included helping visitors gain access to the main source of minerals. The image below shows the site as it was in 2022. The main source of vug deposits was believed to be the “Crystal Bearing Ledge” shown toward the top in the following photo. Bill recommended removing all the surface rocks on the hillside and building an access road below the collecting side and just below the area in the photo below.
Bill also discussed the geologic origins of this steep hillside area, about 150 feet above the nearby river. He pointed out evidence that the topsoil above the crystal laden ledge containing the vug-pocket zone, includes cobblestones and small boulders left behind by the glacial activity. These glacial deposits contain no vugs.
“You will not find ever, any crystals in the glacial fill.”
Readers who want to learn more about the effect which the glacier movements had on the area, please see MSDC's YouTube video of Bill's talk.
The MSDC audience was then treated to a series of short videos of Bill and friends in real time pulling Herkimers from vugs. The snapshot below is from the “Donny Carlin Pocket Reveal and Removal” video.
The snapshot below illustrates the strenuous work required for splitting apart the very hard rock ledge in order to get to the pockets. Joe is seen pounding an industrial strength hammer onto the Leaf Spring Wedges which occasionally broke due to the hardness of the rock and impact of the hammering.
Bill provided references and showed sections of additional videos, including a valuable set of resources that have been provided by Andrew “Rockhound” Eppig and his Dirtman Reports highlighted below.
But wait, there’s more!
Bill used his engineering skills which included taking his own high precision drone LIDAR images of the site updated through 2023 thereby allowing greater understanding the topography of the changing MVMM dig site area and its new road.
For more information on these Herkimer diamond discoveries, geology, and media resources, Bill has provided a paperback co-authored with Daryll Powell now available through Diamond Dan Publications, as noted below. The cost is $16.90 which includes shipping.
Herkules, Medusa and the Baby: The Story of An Historic Discovery in Sprakers New York.
Bill was with Lee Levesque when he discovered these now famous Herkimer giants. Together they have given talks on their adventures, which, on occasion, included the display of the three large Herkimers Lee found as shown below.
With Bill’s presentation being completed, MSDC President Kenny Reynolds thanked Bill for his excellent presentation and opened the floor for a question-and-answer session which added further information and color to an already wonderful program. That Q&A session is at the end of the YouTube video and lasts about 17 minutes.
Readers: We encourage you to visit MSDC’s YouTube channel and view Bill’s presentation in its entirety. You can go to it directly by clicking HERE.
