RocksdayCoal vs Oil Shale
How to tell them apart
A rock formed from buried, compressed plant material — ancient swamp forests turned to stone.
Photo: Amcyrus2012, CC BY 4.0
Fine-grained rock rich in kerogen, an organic material that yields oil when heated.
Photo: Mike Davis, CC0
Quick tests
- Heft: Oil Shale feels noticeably heavier for its size (specific gravity 1.6–2.4 vs 1.1–1.8).
Key differences
- Coal is blacker and lighter.
Side by side
| Property | Coal | Oil Shale |
|---|---|---|
| Type | Sedimentary rock | Sedimentary rock |
| Mohs hardness | 2–3 | 2–3 |
| Luster | Dull to submetallic | Dull to waxy |
| Colors | Black, Brown | Brown, Black, Gray |
| Crystal system / structure | Organic, layered | Fine layered, organic-rich |
| Specific gravity | 1.1–1.8 | 1.6–2.4 |
| Found in | Powder River Basin, Wyoming; Appalachia | Green River Formation, Colorado–Utah–Wyoming; Estonia |
Properties that are the same for both are grayed out.
How to identify coal
- Black and very light for a rock.
- Leaves black dust on hands.
- Layered, with blocky or curved breaks.
- Burns.
Structure: Organic, layered
Full Coal guide →How to identify oil shale
- Brown to black, fine layers.
- Light for a rock.
- Burns or smells of oil when heated.
Structure: Fine layered, organic-rich
Full Oil Shale guide →More comparisons
Could you tell them apart from a blurry close-up?
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