RocksdayDiamond vs Herkimer Diamond
How to tell them apart
Pure carbon crystallized deep in the mantle and carried up in kimberlite eruptions. The hardest natural material.
Photo: DGPC/ADF Luísa Oliveira, CC0
Exceptionally clear, double-terminated quartz crystals that grew in cavities in dolostone.
Photo: Ra'ike (see also: de:Benutzer:Ra'ike), CC BY-SA 3.0
Quick tests
- Hardness: Diamond is clearly harder: Mohs 10 versus 7.
- Streak (rub on unglazed porcelain): Diamond leaves a none (harder than a streak plate) streak; Herkimer Diamond leaves white.
- Heft: Diamond feels noticeably heavier for its size (specific gravity 3.51–3.53 vs 2.65).
Key differences
- Diamond is octahedral and far harder.
Side by side
| Property | Diamond | Herkimer Diamond |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 10 | 7 |
| Luster | Adamantine | Vitreous to brilliant |
| Streak | None (harder than a streak plate) | White |
| Colors | Clear, Yellow, Brown, Gray | Clear |
| Crystal system | Cubic | Trigonal |
| Specific gravity | 3.51–3.53 | 2.65 |
| Formula | C | SiO₂ |
| Found in | Jwaneng, Botswana; Yakutia, Russia | Herkimer County, New York |
Properties that are the same for both are grayed out.
How to identify diamond
- Scratches everything — including corundum.
- Greasy-looking, extremely bright luster even in rough crystals.
- Often octahedral with slightly curved faces.
- Water beads up on its surface.
Crystal system: Cubic
Full Diamond guide →How to identify herkimer diamond
- Water-clear crystals pointed at both ends.
- Short, stubby shape with bright faces.
- Hardness 7 — not a real diamond.
Crystal system: Trigonal
Full Herkimer Diamond guide →More comparisons
Could you tell them apart from a blurry close-up?
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