RocksdayObsidian vs Pitchstone
How to tell them apart
Natural volcanic glass, formed when silica-rich lava cools so fast that crystals have no time to grow.
Photo: Ji-Elle It feels nice and warm It feels like a love storm, CC BY-SA 3.0
Volcanic glass with a dull, resinous shine like pitch — older and more watery than obsidian.
Photo: Alpsdake, CC0
Key differences
- Obsidian is brighter and more glassy.
Side by side
| Property | Obsidian | Pitchstone |
|---|---|---|
| Type | Igneous rock | Igneous rock |
| Mohs hardness | 5–5.5 | 5.5–6 |
| Luster | Glassy | Resinous (pitch-like) |
| Colors | Black, Brown, Red | Black, Green, Brown |
| Crystal system / structure | Glassy | Glassy |
| Specific gravity | 2.35–2.6 | 2.3–2.5 |
| Found in | Glass Buttes, Oregon; Yellowstone, Wyoming | Isle of Arran, Scotland; Isle of Eigg, Scotland |
Properties that are the same for both are grayed out.
How to identify obsidian
- Shiny, glass-like and usually black.
- Curved, shell-shaped (conchoidal) fractures with razor-sharp edges.
- Thin edges are translucent brown or gray.
- May show white 'snowflakes' or a gold/rainbow sheen.
Structure: Glassy
Full Obsidian guide →How to identify pitchstone
- Dark glass with a dull, tar-like luster.
- Often contains small crystals.
- Conchoidal fracture, less sharp than obsidian.
Structure: Glassy
Full Pitchstone guide →More comparisons
Could you tell them apart from a blurry close-up?
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