Specimen at a glance
| Mineral | Quartz (var. Herkimer diamond) |
|---|---|
| Chemistry | SiO2 |
| Mohs hardness | 7 |
| Crystal system | Trigonal |
| Locality | Mohawk Valley, New York |
| Form | Crystal cluster |
| You receive | The exact specimen pictured |
About this specimen
Herkimer diamonds are doubly terminated quartz crystals — not true diamonds — found embedded in dolostone pockets across a limited stretch of New York’s Mohawk Valley, the region that gave the type its name. Unlike most quartz, which grows attached to a rock wall and forms a point at only one end, Herkimer diamonds typically develop freely inside sealed rock cavities, so they crystallize with sharp natural facets and a point on both ends without ever being cut or polished.
This is a matrix specimen — multiple Herkimer points still attached to their original host rock rather than loose, individual crystals — showing lustrous points in warm honey and clear tones across the piece. Herkimer diamonds are known for exceptional clarity at Mohs hardness 7, and matrix pieces like this one are especially valued for showing the crystals exactly as they formed, in place.
Approximately 2.4 x 2″, it’s a strong choice for a New York mineral collection or as a locality-specific gift for anyone who collects by region.
Inside the Herkimer Diamond
Double-terminated, self-formed, and pulled from one small stretch of upstate New York — here’s what makes every piece in this family genuinely rare.
The story: About 500 million years ago, ancient seas laid down the dolostone of the Little Falls Formation across the Mohawk Valley. As the rock later cracked and shifted, silica-rich groundwater seeped into small open pockets and crystallized slowly — with nothing to attach to. That’s the whole secret: most quartz grows welded to a wall and only shows one finished point. A Herkimer diamond floats free in its pocket and grows a sharp termination on both ends, which is why even a small one already looks “finished” straight out of the ground.
Why collectors chase them: True double termination is uncommon in nature, and the exceptional clarity these crystals can reach — combined with a locality that exists nowhere else on Earth in this form — is what separates a “Herkimer” from ordinary quartz. Some carry smoky color, phantom growth lines, or tiny trapped inclusions, so no two parcels ever look quite the same.
Care: At Mohs 7, quartz shrugs off everyday handling, but those double points are genuinely sharp — store loose pieces so the terminations aren’t grinding against each other, and clean with a soft, dry cloth.
Herkimer diamond quartz: the science
- They grew floating in pockets rather than attached to rock, so many formed points on both ends: 18 natural faces with no cutting or polishing.
- The black specks inside are anthraxolite, a solidified hydrocarbon. Researchers describe the mining district as essentially a fossilized oil field.
- The host rock is about 500 million years old, but the quartz grew much later, during the Carboniferous, when mineral-rich basin fluids moved through the dolostone.
Go deeper
Want the full story on Herkimer diamond quartz: how it forms, how to identify it, and what makes a great specimen?
Read Herkimer Diamonds: The Complete Guide Shop all Herkimer Diamond Quartz
Questions about this piece
What is Herkimer diamond quartz?
Herkimer diamonds are not diamonds. They are exceptionally clear, naturally double-terminated quartz crystals that grew loose inside cavities in the Late Cambrian Little Falls Dolostone of New York’s Mohawk Valley.
Where was it found?
This piece comes from Mohawk Valley, New York. We list a locality whenever it is known, because where a mineral formed is part of its story and its value.
How hard is it, and how should I care for it?
It rates 7 on the Mohs scale. At Mohs 7 it is durable, but points and edges chip if they knock against other quartz. Store it separately, rinse in lukewarm water, and keep it away from ultrasonic cleaners and sudden heat.
Is this the exact piece I will receive?
Yes. This listing was photographed individually, and you receive the exact piece shown in the photos.
