RocksdayMoldavite vs Obsidian
How to tell them apart
Bottle-green natural glass created by a meteorite impact in southern Germany about 15 million years ago.
Photo: James St. John, CC BY 2.0
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
Quick tests
- Texture: Obsidian is a rock — a mix of grains or minerals; Moldavite is a single mineraloid.
Key differences
- Obsidian is usually black and has smooth, shell-like breaks.
Side by side
| Property | Moldavite | Obsidian |
|---|---|---|
| Type | Mineraloid | Igneous rock |
| Mohs hardness | 5.5–7 | 5–5.5 |
| Luster | Vitreous | Glassy |
| Colors | Green | Black, Brown, Red |
| Crystal system / structure | Amorphous (impact glass) | Glassy |
| Specific gravity | 2.32–2.38 | 2.35–2.6 |
| Found in | South Bohemia, Czech Republic; Ries crater area, Germany | Glass Buttes, Oregon; Yellowstone, Wyoming |
Properties that are the same for both are grayed out.
How to identify moldavite
- Translucent forest to olive green.
- Deeply sculpted, wrinkled surface.
- Tiny bubbles and swirls inside; fakes are often too clean and evenly colored.
Structure: Amorphous (impact glass)
Full Moldavite guide →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 →More comparisons
Could you tell them apart from a blurry close-up?
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