RocksdayCrocoite vs Realgar
How to tell them apart
A lead chromate forming tangled, vivid orange-red prisms.
Photo: JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 2.5
A bright orange-red arsenic sulfide. Toxic, and it slowly crumbles to yellow powder in light.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Streak (rub on unglazed porcelain): Crocoite leaves a orange-yellow streak; Realgar leaves orange-red.
- Heft: Crocoite feels noticeably heavier for its size (specific gravity 5.9–6.1 vs 3.5–3.6).
Key differences
- Realgar is lighter and resinous.
- Crocoite forms long orange prisms.
Side by side
| Property | Crocoite | Realgar |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 2.5–3 | 1.5–2 |
| Luster | Adamantine | Resinous |
| Streak | Orange-yellow | Orange-red |
| Colors | Orange, Red | Red, Orange |
| Crystal system | Monoclinic | Monoclinic |
| Specific gravity | 5.9–6.1 | 3.5–3.6 |
| Formula | PbCrO₄ | As₄S₄ |
| Found in | Dundas, Tasmania; Berezovsk, Ural Mountains, Russia | Getchell mine, Nevada; Shimen, Hunan, China |
Properties that are the same for both are grayed out.
How to identify crocoite
- Long, slender, bright orange prisms.
- Fragile and heavy.
- Orange-yellow streak.
Crystal system: Monoclinic
Full Crocoite guide →How to identify realgar
- Orange-red with a resinous luster.
- Very soft.
- Orange streak; often with yellow orpiment.
Crystal system: Monoclinic
Full Realgar guide →More comparisons
Could you tell them apart from a blurry close-up?
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