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Source: United States
Chemical: HgS (Mercury Ore)
Crystal System: Trigonal
Formation: Volcanic craters and hydrothermal environments such as hot springs. It can form in conjunction with dolomites as shown in the photograph below.
Unusual Properties: Although cinnabar is sometimes used as carved ornamental beads, this is a dangerous mineral due to its high mercury content. In fact, the method for extracting mercury from cinnabar is to heat the mineral to a temperature of only about 400F and the crystallized mercury will turn into a gaseous form. This gas is then put through a process of condensation to produce a liquid state which produces liquid mercury....used in thermometers for many decades.
Unfortunately, mercury poisoning has become a serious problem to the environment, and use of this mineral for anything other than scientific or collectors purposes should be seriously considered for environmental reasons.


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International School of Gemology.