Orpiment
>
Orpiment, also known as ″yellow arsenic blende″ is a deep-colored, orange-yellow arsenic sulfide mineral with formula As
₂S
₃. It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and may be formed through... Wikipedia
Birefringence: δ = 0.620
Category: Sulfide mineral
Cleavage: Perfect on, imperfect on
Color: Lemon-yellow to golden or brownish yellow
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal system: Monoclinic
Diaphaneity: Transparent