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TitleAlacranite, As4S4: a new occurrence, new formula, and determination of the crystal structure
AuthorBurns, P C; Percival, J BORCID logo
SourceCanadian Mineralogist vol. 39, 2001 p. 809-818,
Alt SeriesGeological Survey of Canada, Contribution Series 1999253
PublisherMineralogical Association of Canada
Mediapaper; on-line; digital
File formatpdf
Lat/Long WENS 146.0000 154.0000 -1.0000 -7.0000
Subjectsigneous and metamorphic petrology; mineralogy; metallic minerals; geochemistry; marine geology; polymetallic ores; sulphides; arsenic; realgar; vein deposits; veins; pyrite; sphalerite; galena; chalcopyrite; sulphosalts; epithermal deposits
Illustrationslocation maps; photographs; photomicrographs; tables; schematic diagrams
Released2001 06 01
AbstractBetween July 20 and August 3, 1998, cruise SO-133 aboard the R/V Sonne completed detailed mapping and sampling of the seafloor around Lihir Island in Papua New Guinea. Sampling of Conical Seamount resulted in the discovery of an unusual occurrence of alacranite and realgar associated with polymetallic vein mineralization consisting of pyrite, sphalerite, galena, minor chalcopyrite and sulfosalts, along with intense clay and silica (amorphous) alteration. Alacranite occurs as subhedral to euhedral tabular orange crystals that are transparent to translucent with a vitreous to resinous luster. Crystals occur both isolated and as groupings within vugs and on matrix, and have a maximum length of 0.1 mm. Single-crystal diffraction data were collected using MoK\'01 X-radiation and a CCD-based detector. The structure is monoclinic, space group C2/c, a 9.943(1), b 9.366(1), c 8.908(1) Å, \'02 102.007(2)°, and was refined to an agreement index (R1) of 6.6%. The structure determination indicates that the formula of alacranite is As4S4, Z = 4, rather than As8S9 as reported earlier from a Russian locality. Thus, alacranite is the third polymorph of this composition, after realgar and pararealgar. The structure contains covalently bonded As4S4 molecules that are linked by van der Waals forces to form the three-dimensional structure. The structure is identical to that of synthetic alpha-As4S4.

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