Cinnabar on dolomite (Hunan, China)
Cinnabar on dolomite from China. (public display, Dwyer Mercer County District Library, Celina, Ohio, USA)
Red = cinnabar
Whitish = dolomite (CaMg(CO3)2 - calcium magnesium carbonate)
A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5200 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.
The sulfide minerals contain one or more sulfide anions (S-2). The sulfides are usually considered together with the arsenide minerals, the sulfarsenide minerals, and the telluride minerals. Many sulfides are economically significant, as they occur commonly in ores. The metals that combine with S-2 are mainly Fe, Cu, Ni, Ag, etc. Most sulfides have a metallic luster, are moderately soft, and are noticeably heavy for their size. These minerals will not form in the presence of free oxygen. Under an oxygen-rich atmosphere, sulfide minerals tend to chemically weather to various oxide and hydroxide minerals.
Cinnabar is a mercury sulfide mineral (HgS). It is one of the few sulfide minerals that lacks a metallic luster (other examples are orpiment & realgar). In its crystalline form, cinnabar has an intense adamantine luster. Massive, fine-grained specimens generally have an earthy luster. Cinnabar has a reddish color reddish streak, 3 different cleavage planes, is quite soft (H = 2 to 2.5), and is heavy for its size (high specific gravity).
Cinnabar principally occurs in some young volcanic rocks and hydrothermal spring deposits. It's a fairly volatile chemical - much of it passes out from volcanic vents into the atmosphere as a gas.
Cinnabar is the most important ore mineral for the element mercury and was long used as a red pigment.
Locality: Hunan Province, southern China
Photo gallery of cinnabar: