Realgar is also known as ‘cockscomb stone’. Its composition is AsS, and it is an important arsenic mineral. It contains 70.1% arsenic and belongs to the monoclinic crystal system. The crystals are short columns, and the crystal surfaces are striped with longitudinal striations. The aggregates are granular, dense or blocky but sometimes appear as soil-like blocks or crust-like aggregates. It is bright red to orange with orange to red streaks and has transparent to translucent diaphaneity, a resinous to greasy lustre, a specific gravity of 3.56, a Mohs hardness of 1.5–2 and conchoidal fractures. Its melting point is very low (310 °C), and it emits a garlic odour when burned. It is a low-temperature hydrothermal mineral and often coexists with orpiment and stibnite. It is an important raw material for the extraction of arsenic. It is a common pigment, and realgar crystals are also important ornamental stones.