In Chinese, cinnabar is also known as ‘red sand’. Its content is mainly HgS, and it is an important mercury mineral ore. It contains 86.2% mercury and belongs to the trigonal crystal system. The crystals appear as thick plates or are rhombohedral or columnar. Crystal twinning is common. Cinnabar also appears as blocky, shell-like or granular aggregates. The typical colours are brownish red or scarlet with scarlet streaks. It has transparent to opaque diaphaneity, an adamantine, submetallic or dark lustre, a specific gravity of 8.0–8.2, a Mohs hardness of 2.5, and conchoidal to uneven fractures. It usually forms in low-temperature hydrothermal veins or sedimentary rocks associated with volcanic activity. Cinnabar is an important ore for the extraction of mercury, and it is also an important pigment. It can also be used as a fine ornamental rock.