Stibnite
Stibnite is antimony sulfide, the chief ore of antimony. It is famous for brilliant steel-gray metallic crystals that form long, slender, often curved or radiating prismatic blades with perfect lengthwise cleavage.
Stibnite properties at a glance
| Type | Sulfide Minerals |
|---|---|
| Chemical formula | Sb2S3 |
| Mohs hardness | 2 |
| Crystal system | orthorhombic |
| Luster | metallic |
| Streak | Lead gray |
| Cleavage | Perfect lengthwise |
| Fracture | Subconchoidal |
| Specific gravity | 4.6 |
| Transparency | opaque |
| Common colors | Lead gray, Steel gray, Silvery gray |
| Rarity | uncommon |
Geology & background
Stibnite forms in low-temperature hydrothermal veins and hot-spring deposits and is the most important ore mineral of antimony.
Stibnite has been used since antiquity as a source of antimony and as a black eye cosmetic, and modern mining of the mineral supplies antimony for alloys, batteries, and flame retardants.
How to identify Stibnite
- 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.
Where Stibnite is found
Stibnite occurs in low-temperature hydrothermal veins, with notable specimen localities in China, Japan, Romania, Bolivia, France, and the United States.
How much is Stibnite worth?
| Entry-level specimen | $10 |
|---|---|
| Typical collector specimen | $120 |
| Premium specimen | $1500+ |
Value depends on crystal size, luster, intactness of blades, locality, and overall aesthetics.
Common uses
- Primary ore of antimony
- Antimony alloys and flame retardants
- Historic cosmetic and pigment material
- Collector specimens
Interesting facts
- Spectacular stibnite clusters from the Ichinokawa Mine in Japan are among the most prized mineral specimens ever found.
- Powdered stibnite was used in antiquity as the dark cosmetic kohl.
- Stibnite is soft enough to be scratched by a fingernail in some cases and bends easily.
- Antimony from stibnite has long been used to harden lead alloys and as a flame retardant.
Care & safety
Stibnite is very soft, brittle, and easily bent or scratched, so blades damage readily.
Contains antimony. Stibnite contains antimony; wash hands after handling, keep it away from food, and do not ingest material.
Avoid inhaling dust. Do not cut, grind, or polish specimens without eye protection and a proper respirator.
