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User:Dwwashburn/Dimorphite

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dimorphite
General
CategoryMineral
Formula
(repeating unit)
As4S3
Crystal systemorthrhombic dipyramidal
Identification
Formula mass395.88 g/mol
Colororange-yellow
Cleavagenone
Fracturebrittle
Mohs scale hardness1.5 (between talc and gypsum)
Lusteradamantine
Streakyellow
Diaphaneitytransparent
Density3.59 g/cm3 (avg)
Optical propertiesbiaxial
Dispersionstrong
Ultraviolet fluorescencenone
Other characteristicsburns without residue
References[1][2][3]

Dimorphite (chemical name tetraarsenic trisulfide) is a very rare orange-yellow chalcogenide mineral, related to realgar. In nature, dimorphite forms primarily by deposit in volcanic fumaroles at temperatures of 70°-80°C (158°F-176°F). Dimorphite was first discovered in a such a fumarole near Naples, Italy in 1849 by the mineralologist Arcangelo Scacchi (1810-1893). Since its discovery, dimorphite has only been found elsewhere in the Alacrán silver mine near Copiapó, Chile.[2] However, dimorphite can be synthesized by melting arsenic and sulfur together in the proper molar ratios in vacuum.[4]

Interesting Properties and Applications

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Dimorphite has two crystal forms, α- and β-. This property gives rise to its name, which comes from the Greek for "two" and "form." Dimorphite transitions between its α- and β- forms at around 130°C (266°F).[4]

Initial research done by professors from the Technical University of Moldova and the Universität der Bundeswehr München indicates the possibility of using dimorphite in the development of gas sensors[5][6], due to the semiconductive properties of dimorphite. Dimorphite also reacts with sulfur in carbon disulfide (CS2) to form tetraarsenic tetrasulfide[4] (realgar), a major source of arsenic and a component in some fireworks.

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  • Image of dimorphite sample (image available freely for educational use only) here.

References

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  1. ^ "Dimorphite: Dimorphite mineral information and data". Mindat.org - the mineral and locality database. Retrieved 2009-03-10.
  2. ^ a b Anthony, John W. (2003). "Dimorphite" (PDF). Handbook of Mineralogy. Tucson, AZ: Mineral Data Publishing. Retrieved 2009-03-10. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ David Barthelmy. "Dimorphite Mineral Data". Mineralogy Database. Retrieved 2009-03-10.
  4. ^ a b c Wiberg, Egon, Nils Wiberg, and Arnold Frederick Holleman. Inorganic Chemistry. San Diego: Academic Press, 2001.
  5. ^ Tsiulyanu, D.; Golbam, G.; Kolomeyho, E.; Melnic, O. (1996), "Photoconductivity and optical absorption of dimorphite thin films", Physica Status Soldi. B., 197 (1): 61–64, doi:10.1002/pssb.2221970110
  6. ^ Marian, S.; Potje-Kamloth, K.; Tsiulyanu, D.; Liess, H. -D. (2000), "Dimorphite based gas sensitive thin films", Thin Solid Films, 359 (1): 108–112, doi:10.1016/S0040-6090(99)00707-5