The most striking property of cinnabar is its red color. Its bright color makes it easy to spot in the field and is a fascination for those who discover it. It has a Mohs hardness of 2 to 2.5 and is very easily ground into a very fine powder. It has a specific gravity of 8.1, which is extremely high for a nonmetallic mineral.
The luster of cinnabar ranges from dull to adamantine. Specimens with a dull luster are usually massive, contain abundant impurities and do not have the brilliant red color of pure cinnabar. Adamantine specimens are usually the rarely found crystals.
| Physical Properties of Cinnabar | |
| Chemical Classification | Sulfide |
| Color | Bright red to brownish red, sometimes gray |
| Streak | Red |
| Luster | Adamantine to dull |
| Diaphaneity | Transparent, translucent, or opaque |
| Cleavage | Perfect, prismatic |
| Mohs Hardness | 2 to 2.5 |
| Specific Gravity | 8 to 8.2 |
| Diagnostic Properties | Specific gravity, color, streak, cleavage, association with volcanic activity, association with other sulfide minerals. |
| Chemical Composition | Mercury sulfide, HgS |
| Crystal System | Trigonal |
| Uses | The only important ore of mercury. Its use as a pigment, collector’s gem, and ornamental carving material has declined due to toxicity. |