Dimorphite

Dimorphite
General
CategorySulfide mineral
Formula
(repeating unit)		As4S3
IMA symbolDim[1]
Strunz classification2.FA.10
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma
Unit cella = 11.24, b = 9.90
c = 6.56 [Å]; Z = 4
Identification
Formula mass395.88 g/mol
Colororange-yellow
Crystal habitGroups of pyramidal crystals
Cleavagenone
Fracturebrittle
Mohs scale hardness1.5
Lusteradamantine
Streakyellow
Diaphaneitytransparent
Specific gravity3.59
Optical propertiesBiaxial (+)
Dispersionstrong
Ultraviolet fluorescencenone
Other characteristicsburns without residue
References[2][3][4]

Dimorphite, chemical name arsenic sesquisulfide (As4S3), is a very rare orange-yellow arsenic sulfide mineral. In nature, dimorphite forms primarily by deposition in volcanic fumaroles at temperatures of 70–80 °C (158–176 °F). Dimorphite was first discovered in such a fumarole near Naples, Italy in 1849 by the mineralogist Arcangelo Scacchi (1810–1893).[5] Since its discovery, dimorphite has been found in the Alacrán silver mine near Copiapó, Chile.[3] It has also been reported from Cerro de Pasco, Peru, and the Lavrion District Mines in Attica, Greece.[2]

Properties and applications

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).[6]

Dimorphite can be synthesized by melting arsenic and sulfur together in the proper molar ratios in vacuum.[6]

Initial research indicates the possibility of using synthetic dimorphite in the development of gas sensors,[7][8] due to the semiconductive properties of dimorphite.

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b Dimorphite mineral information and data Mindat.org
  3. ^ a b Handbook of Mineralogy
  4. ^ Webmineral data
  5. ^ Guarini G, Palmieri L, Scacchi A (1855) Chapter 5. Esame mineralogico-chimico delle produzioni dell'incendio, in Memoria sullo Incendio Vesuviano, Gaetano Nobile (Napoli) p. 165-200
  6. ^ a b Wiberg, Egon, Nils Wiberg, and Arnold Frederick Holleman. Inorganic Chemistry. San Diego: Academic Press, 2001.
  7. ^ Tsiulyanu, D.; Golbam, G.; Kolomeyho, E.; Melnic, O. (1996). "Photoconductivity and optical absorption of dimorphite thin films". Physica Status Solidi B. 197 (1): 61–64. Bibcode:1996PSSBR.197...61T. doi:10.1002/pssb.2221970110.
  8. ^ Marian, S.; Potje-Kamloth, K.; Tsiulyanu, D.; Liess, H. -D. (2000). "Dimorphite based gas sensitive thin films". Thin Solid Films. 359 (1): 108–112. Bibcode:2000TSF...359..108M. doi:10.1016/S0040-6090(99)00707-5.