RocksdayJet vs Lignite
How to tell them apart
A hard, compact black lignite — fossil wood — that takes a mirror polish.
Photo: Geni, CC BY-SA 4.0
Soft brown coal, the youngest and lowest grade, often with visible woody texture.
Photo: James St. John, CC BY 2.0
Quick tests
- Hardness: Jet is clearly harder: Mohs 2.5–4 versus 1–2.
- Texture: Lignite is a rock — a mix of grains or minerals; Jet is a single mineraloid.
Key differences
- Jet is a hard, polishable form of lignite.
Side by side
| Property | Jet | Lignite |
|---|---|---|
| Type | Mineraloid | Sedimentary rock |
| Mohs hardness | 2.5–4 | 1–2 |
| Luster | Velvety to vitreous (polished) | Dull |
| Streak | Brown | — |
| Colors | Black | Brown, Black |
| Crystal system / structure | Amorphous (organic) | Organic, woody |
| Specific gravity | 1.3–1.4 | 1.1–1.3 |
| Found in | Whitby, England; Asturias, Spain | Rhineland, Germany; Latrobe Valley, Australia |
Properties that are the same for both are grayed out.
How to identify jet
- Jet black, light and warm to the touch.
- Brown streak.
- Smells like coal when a hot needle touches it.
Structure: Amorphous (organic)
Full Jet guide →How to identify lignite
- Brown-black and crumbly.
- Wood grain sometimes visible.
- Very light; cracks as it dries.
Structure: Organic, woody
Full Lignite guide →More comparisons
Could you tell them apart from a blurry close-up?
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