Specimen at a glance
| Mineral | Quartz (var. Herkimer diamond) |
|---|---|
| Chemistry | SiO2 |
| Mohs hardness | 7 |
| Crystal system | Trigonal |
| Locality | New York (Herkimer district) |
| Form | Crystal cluster |
| You receive | The exact specimen pictured |
About this specimen
“Herkimer diamonds” are doubly-terminated quartz crystals famously found in vugs within the Cambrian-age Little Falls Dolostone of central New York’s Mohawk Valley — quartz that grew freely in open cavities within the dolostone, with no attachment point, letting it form points on both ends rather than the single termination typical of quartz grown from a base. This specimen is a small druzy cluster in that same style, with numerous sharp, lustrous points across its surface.
What makes this piece a little different from a typical Herkimer cluster is the cream-colored, blocky feldspar crystals grown directly through the quartz druzy — a mineral pairing that shows both were crystallizing in the same cavity environment. The contrast between the water-clear to smoky quartz points and the opaque, angular feldspar makes for good textural variety on a single piece.
True Herkimer diamonds and Herkimer-style quartz score a 7 on the Mohs scale, making them durable for handling, though individual druzy points can snap off under pressure — handle by the base/matrix rather than gripping the crystal faces. Clean with a soft brush or cloth; ultrasonic cleaners are not recommended given the delicate points.
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 New York (Herkimer district). 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.
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