Category Archives: Mineralogy and Petrology

Cinnabar: An attractive but extremely toxic mineral

Cinnabar is a Mercury Sulphide mineral with a chemical formula HgS. It has a bright red colour and a Moh’s hardness of 2-2.5. Cinnabar was originally used as a pigment and cut into jewellery. However, due to its toxicity, these uses have been discontinued.

Cinnabar is a hydrothermal mineral precipitating from ascending hot waters through fissures and forms at low temperatures of less than 200 degree centigrade and at shallow depths. It is associated with Igneous Rocks.

Currently, Cinnabar is used an an ore of Mercury, where its powder is heated in a kiln and mercury vapour sublimes.

cinnabarMetacinnabar is a polymorph of cinnabar. It has the same chemical composition (HgS) as cinnabar but a different crystal structure. Cinnabar is trigonal, while metacinnabar is isometric. The two minerals should not be confused with one another because metacinnabar has a metallic gray color, a gray-to-black streak and a metallic-to-submetallic luster.

Other forms of cinnabar are:

  • Hepatic cinnabar or paragite is an impure brownish variety from the mines of Idrija in the Carniola region of Slovenia, in which the cinnabar is mixed with bituminous and earthy matter.
  • Hypercinnabar, crystallizes at high temperature in the hexagonal crystal system.
  • Metacinnabar is a black-colored form of mercury(II) sulfide, which crystallizes in the cubic crystal system.
  • Synthetic cinnabar is produced by treatment of mercury(II) salts with hydrogen sulfide to precipitate black, synthetic metacinnabar, which is then heated in water. This conversion is promoted by the presence of sodium sulfide.

More information about cinnabar found in: https://geology.com/minerals/cinnabar.shtml

Did you know that Cinnabar means Dragon’s blood?