What is Realgar?
[[File:Realgar-realgarb.jpg|thumb|Realgar]] '''Realgar''' is a [[mineral]]. Its chemical formula is As<sub>4</sub>S<sub>4</sub>. It is a soft ([[Mohs hardness]] 1.5 to 2) red mineral. It is an [[ore]] of [[arsenic]]. It changes into a yellow powder when exposed to light. This yellow powder is called '''pararealgar'''. It melts at 320°C and burns with a blue flame, making arsenic and [[sulfur]] fumes. It was used to make a white color in [[fireworks]] before powdered [[metal]]s were used. It is still used in some crackling firecrackers. It was used as a red [[pigment]] and an item of [[trade]]. It is used as a [[medicine]] in [[China]]. Its uses are similar to [[orpiment]], a similar mineral. [[Category:Minerals]]