RocksdayOrpiment vs Sulfur
How to tell them apart
A golden-yellow arsenic sulfide with a pearly sheen. Toxic.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
A native element that crystallizes around volcanic vents and in salt domes. Unmistakably bright yellow.
Photo: Ivar Leidus, CC BY-SA 4.0
Quick tests
- Streak (rub on unglazed porcelain): Orpiment leaves a pale yellow streak; Sulfur leaves white to pale yellow.
- Heft: Orpiment feels noticeably heavier for its size (specific gravity 3.49 vs 2.07).
Key differences
- Sulfur is paler, lighter and burns with a blue flame.
Side by side
| Property | Orpiment | Sulfur |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 1.5–2 | 1.5–2.5 |
| Luster | Resinous to pearly | Resinous |
| Streak | Pale yellow | White to pale yellow |
| Colors | Yellow, Orange | Yellow |
| Crystal system | Monoclinic | Orthorhombic |
| Specific gravity | 3.49 | 2.07 |
| Formula | As₂S₃ | S |
| Found in | Getchell mine, Nevada; Quiruvilca, Peru | Kawah Ijen, Indonesia; Agrigento, Sicily |
Properties that are the same for both are grayed out.
How to identify orpiment
- Lemon to golden yellow with a pearly cleavage face.
- Flexible flakes.
- Very soft.
Crystal system: Monoclinic
Full Orpiment guide →How to identify sulfur
- Bright lemon yellow.
- Very light and soft.
- Smells like rotten matches when warmed or rubbed.
- Melts and burns with a blue flame.
Crystal system: Orthorhombic
Full Sulfur guide →More comparisons
Could you tell them apart from a blurry close-up?
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