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Realgar (Photo) [abbr. Rlg ]

Year of discovery: before 13th century (Wolrd), 1877 (Japan)

Locality list: 61 localities of realgar

• AsS
• α-[As₄S₄]

• Class: Realgar group
• Class: Sulfide
• Insoluble in: HCl
• Lightfastness: Photodissociate to Arsenolite and Orpiment.
• Lightfastness: Phase transit by light exposure to Pararealgar.

• Polymorph: Alacránite (Alacranite) (β, Monoclinic), Pararealgar (γ, Monoclinic)

• Color: Dark red, Orange
• Tarnish: Dull luster
• Streak: Orange, Red
• Luster: Resinous
• Diaphaneity: Transparent

• Habit: Short Prismatic elongated to [001]
• Striation: [001]
• Twin: {100} contact

• Cleavage: Good on {010} (1 plane), Distinct on {-101}, {100}, {120}, and {110} (6 planes)
• Hardness: 1.5-2
• Density: 3.6

• System: Monoclinic
• Group: 2/m, P2₁/n
• Lattice: a=9.3, b=13.6, c=6.6, β=106.4

Etymology: Rahj-al-ghar (Powder in mine) in Arabic