Massive Orpiment with minor amounts of Realgar.
CHEMISTRY As2S3 Arsenic sulfide
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Crystals of Orpiment are rare but are normally short prismatic and pseudo orthorhombic. Orpiment is normally massive or foliated but can be reniform or botryoidal and even granular.
COLOR AND OTHER OPTICAL PROPERTIES Yellow, light yellow to golden yellow and brownish yellow
HARDNESS 1.5 - 2
SPECIFIC GRAVITY 3.5
LUSTER Resinous to pearly on cleavage faces
STREAK Light yellow
BREAKABILITY Cleavage very good in one direction producing a flaky surface, sectile
OCCURRENCE Orpiment is a low temperature hydrothermal deposit found associated with hot springs. It is a common alteration product of other arsenic minerals. It is also found as a sublimation deposit associated with fumaroles and mine fires.
ASSOCIATED MINERALS - Realgar