Mineral Information and Data:

As8S9 [CNMNC approved formula]

Named for the occurrence in the Alacran deposit, Chile.

IMA status : Approved Species 1985 (IMA1985-033)
(8th edition) :  
  (02) Sulfides - Including Selenides and Tellurides
  (02.08) where Am Bn Xp, with (m+n):p=1:1
  (02.08.22) Realgar Series
(10th edition) :
  (02) Sulfides
  (02.F) Sulfides of Arsenic, Alkalies; Sulfides with Halide, Oxide, Hydroxide, H2O
  (02.FA) With As, (Sb), S
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 9.89 Å, b = 9.73 Å, c = 9.13 Å, b = 101.84°
Crystal Habit: Grains flattened and prismatic, to 0.5 mm
Color: Orange-yellow, orange
Diaphaneity: Transparent
Luster: Adamantine, greasy
Hardness (Mohs): 1.5
Measured Density: 3.43 g/cm3
Cleavage: Imperfect on {100}
Tenacity: Very brittle
Fracture: Conchoidal
Streak: Orange-yellow
Polymorphism and Series: Trimorphous with pararealgar and realgar.
Geologic Setting: In hydrothermal As–S veins (Alacran mine, Chile); in the condensation zone of a hydrothermal Hg–Sb–As system as cement in a sandy gravel (Uzon caldera, Russia); formed at low temperatures in a polymetallic hydrothermal deposit on a submarine seamount (Conical Seamount, Papua New Guinea).
Mineral Association: Realgar, orpiment, arsenic, sulfur, stibnite, pyrite, greigite, arsenopyrite, arsenolamprite, sphalerite, acanthite, barite, quartz, calcite (Alacran mine, Chile); realgar, orpiment, uzonite, stibnite, cinnabar, pyrite, sulfur (Uzon caldera, Russia); realgar, pyrite, sphalerite, galena, chalcopyrite, amorphous silica (Conical Seamount, Papua New Guinea).


Origin: Katerina Coal Mine, Radvanice, Trutnov, Hradec Králové Region, Bohemia (Böhmen; Boehmen), Czech Republic
Sample size: 3.8 x 4.3 x 2.8 cm
Photo: Dan Weinrich


(zoom-in of above)