Identification guide · Native Elements
How to Identify Sulfur
Sulfur is usually yellow, bright yellow, and yellowish brown with a resinous luster and is transparent. It has a Mohs hardness of 2. A fingernail (Mohs 2.5) scratches it easily. Its streak is white to pale yellow. It is most often confused with Amber, Calcite, and Gypsum; the tests below separate them.
Sulfur identification checklist
| Color | Yellow, Bright yellow, Yellowish brown, Greenish yellow | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Resinous | Compare a fresh surface with glass and metal; this luster is softer than either. |
| Transparency | Transparent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 2 | A fingernail (Mohs 2.5) scratches it easily. |
| Streak | White to pale yellow | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Imperfect | |
| Fracture | Conchoidal to uneven | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.07 | Noticeably light in the hand for its size (specific gravity about 2.07). |
| Crystal system | Orthorhombic |
Sulfur look-alikes and how to tell them apart
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Sulfur vs Amber →
Calcite is harder (Mohs 3) than Sulfur (Mohs 2), so Calcite will scratch Sulfur and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Sulfur vs Calcite →
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Sulfur vs Gypsum →
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Field tips
- Look for bright yellow color, resinous luster, and very low hardness near 2 that a knife scratches easily.
- Low density and a faint sulfur odor when freshly broken or warmed are strong clues.
- Occurrence near volcanic vents, hot springs, or salt domes supports the identification.
Sulfur identification FAQ
How can you tell if a rock is Sulfur?
Check the color (yellow, bright yellow, yellowish brown, and greenish yellow), the resinous luster, a Mohs hardness of 2 and a white to pale yellow streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Sulfur?
Sulfur has a Mohs hardness of 2. A fingernail (Mohs 2.5) scratches it easily.
What is the difference between Sulfur and Amber?
Sulfur (Mohs 2, resinous luster) and Amber (Mohs 2.5, resinous luster) look alike, but hardness, streak and heft usually separate them. See the full Sulfur vs Amber comparison for a side-by-side table.
Is Sulfur worth anything?
Entry-level Sulfur specimens sell for around $5, typical collector pieces about $35, and premium examples $250 or more depending on size, quality and locality.
What color is Sulfur?
Sulfur is most often yellow, bright yellow, yellowish brown, and greenish yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
