Alacranite
As8S9 [CNMNC approved formula]
Named for the occurrence in the Alacran deposit, Chile.
| IMA status : | Approved Species 1985 (IMA1985-033) |
| CLASSIFICATION | |
| Dana (8th edition) : |
02.08.22.04 |
| (02) Sulfides - Including Selenides and Tellurides | |
| (02.08) where Am Bn Xp, with (m+n):p=1:1 | |
| (02.08.22) Realgar Series | |
| Nickel-Strunz (10th edition) : |
02.FA.20 |
| (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 RepublicSample size: 3.8 x 4.3 x 2.8 cm
Photo: Dan Weinrich
(zoom-in of above)