Specimen at a glance
| Mineral | Quartz (var. Herkimer diamond) |
|---|---|
| Chemistry | SiO2 |
| Mohs hardness | 7 |
| Crystal system | Trigonal |
| Locality | New York (Herkimer district) |
| Form | Druzy |
| You receive | The exact specimen pictured |
About this specimen
A glittering plate of tiny Herkimer “diamond” quartz crystals forming a druzy crust over gray matrix, from New York. The crystals are small but extremely bright, giving the whole surface a frosted sparkle under light.
Herkimer “diamonds” are not diamonds at all — they are an exceptionally clear, naturally double-terminated variety of quartz found in cavities (vugs) within the Cambrian-age Little Falls Dolomite of the Mohawk Valley region of New York. Because they grew suspended in open pockets rather than attached to a wall, many crystals developed points at both ends and formed with naturally brilliant faces that need no cutting or polishing.
The original collector label reads: Herkimer “Diamond” Crystal Quartz Druzy Cluster, locality “Crystal Grove? Frank J McGovern, New York” — the specific mine attribution is marked with a question mark on the label, so we list it simply as New York. Lot #20.
Care
Quartz is Mohs 7 and very durable, but terminations and edges can chip if knocked against harder surfaces. Dust with a soft brush; rinse in lukewarm water if needed and air dry. Avoid sudden temperature changes.
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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