Herkimer Diamonds

July 19, 2020

Far from being a real diamond, but could you image breaking into rock and seeing a small cavity containing a perfectly formed, highly lustrous, sharp edged, clear and colourless crystal? You’d think you hit the jackpot and found diamonds I’m sure of it.

The Herkimer Diamond is named after the Herkimer County in New York U.S.A where they were discovered, these doubly terminated crystals are actually quartz. The “Little Falls” Dolostone matrix in which they are found is dated back to Precambrian times over 500 million years ago. In fact, the Mohawk people would use Herkimer Diamonds to make tools and trade with other tribes. However, as the European glass era arrived in the early 1600’s the interest in Herkimer Diamonds started to disappear. Although named after Herkimer County, Herkimer Diamonds are also found in Tibet, Afghanistan, Norway and various other world locations.

Forming at the bottom of a shallow sea in its beginnings, dolostone was subject to centuries of deep burial under sedimentation to a depth of five kilometres and a steady increase of temperatures upwards of 175 degrees. Gradually, the silica contents in the organic material and other chemical constituents started to dissolve through extremely slow cooling and began to crystallise. The general rule of thumb for a crystal is the slower the cooling of the solution, the slower the crystallisation process and the bigger the crystals.

The name “diamond” was adopted as a nod to their amazing clarity and precise formation. Although this is what is expected of diamond crystals, often they aren’t so perfectly formed and certainty the clarity is another great challenge. Upon further inspection there are some clear factors that separate Herkimer Diamonds from the real deal. Herkimer Diamonds display typical quartz crystal characteristics; 6 prisms, two terminations each with 3 major and 3 minor rhombohedra. Their hardness is 7, compared to the highest ranking of 10 of a diamond. Common inclusions found are two or three-phase inclusions, negative crystals (exhibiting quartz forms), healed fractures (sometimes with yellow iron staining) and flakes of black hydrocarbon.

Bunny Bedi, owner and director at Made In Earth, talks about his passion for these remarkable crystals.

“Herkimer Diamonds, although simple double terminated quartz crystals, are just fascinating! We always show our clients a specimen of crystal in matrix to help explain how they are found and just how incredible they look poking out of a cavity of dolostone. Knowing how the crystals form is important in helping explain why most Herkimer Diamonds have an indentation or rough surface over one or several crystal faces. This is the breaking point where the crystals have been dislodged from the matrix and is evidence of where they once lived.”

They may not have had the same formations or hardness as a diamond, nor the hefty price tag, but Herkimer Diamonds are enchanting and distinguished in their own right. I suppose, technically we cannot call them diamonds, but I think there’s something more extraordinary about these crystals than conventional quartz and so the name is fitting.

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