Identification guide · Sulfide Minerals
How to Identify Stibnite
Stibnite is usually lead gray, steel gray, and silvery gray with a metallic luster and is opaque. It has a Mohs hardness of 2. A fingernail (Mohs 2.5) scratches it easily. Its streak is lead gray. It is most often confused with Molybdenite, Cinnabar, and Realgar; the tests below separate them.
Stibnite identification checklist
| Color | Lead gray, Steel gray, Silvery gray | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Metallic | Turn it under a lamp: a true metallic shine reflects like polished metal and stays opaque at thin edges. |
| Transparency | Opaque | 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 | Lead gray | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Perfect lengthwise | |
| Fracture | Subconchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 4.6 | Very heavy, metallic heft (specific gravity about 4.6). |
| Crystal system | Orthorhombic |
Stibnite 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. Stibnite vs Molybdenite →
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Stibnite vs Cinnabar →
Both sit near Mohs 2, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Stibnite vs Realgar →
Pyrite is harder (Mohs 6.5) than Stibnite (Mohs 2), so Pyrite will scratch Stibnite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
Field tips
- Look for bright metallic steel-gray prismatic blades, often curved or radiating, with striations along their length.
- Very low hardness near 2 and perfect lengthwise cleavage are strong identifying features.
- A lead-gray streak and high density help separate stibnite from similar gray metallic minerals.
Stibnite identification FAQ
How can you tell if a rock is Stibnite?
Check the color (lead gray, steel gray, and silvery gray), the metallic luster, a Mohs hardness of 2 and a lead gray streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Stibnite?
Stibnite has a Mohs hardness of 2. A fingernail (Mohs 2.5) scratches it easily.
What is the difference between Stibnite and Molybdenite?
Stibnite (Mohs 2, metallic luster) and Molybdenite (Mohs 1.25, metallic luster) look alike, but hardness, streak and heft usually separate them. See the full Stibnite vs Molybdenite comparison for a side-by-side table.
Is Stibnite worth anything?
Entry-level Stibnite specimens sell for around $10, typical collector pieces about $120, and premium examples $1500 or more depending on size, quality and locality.
What color is Stibnite?
Stibnite is most often lead gray, steel gray, and silvery gray. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
