Dimorphite

Dimorphite
General
Category	Sulfide mineral
Formula; (repeating unit)	As4S3
Strunz classification	2.FA.10
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) ; H-M symbol: (2/m 2/m 2/m)
Space group	Pnma
Unit cell	a = 11.24, b = 9.90 ; c = 6.56 [Å]; Z = 4
Identification
Formula mass	395.88 g/mol
Color	orange-yellow
Crystal habit	Groups of pyramidal crystals
Cleavage	none
Fracture	brittle
Mohs scale hardness	1.5
Luster	adamantine
Streak	yellow
Diaphaneity	transparent
Specific gravity	3.59
Optical properties	Biaxial (+)
Dispersion	strong
Ultraviolet fluorescence	none
Other characteristics	burns without residue
References	[1][2][3]

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 mineralologist Arcangelo Scacchi (1810–1893).[4] Since its discovery, dimorphite has been found in the Alacrán silver mine near Copiapó, Chile.[2] It has also been reported from Cerro de Pasco, Peru, and the Lavrion District Mines in Attica, Greece.[1]

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).[5]

Dimorphite can be synthesized by melting arsenic and sulfur together in the proper molar ratios in vacuum.[5]

Initial research indicates the possibility of using synthetic dimorphite in the development of gas sensors,[6][7] due to the semiconductive properties of dimorphite.

References

Dimorphite mineral information and data Mindat.org
Handbook of Mineralogy
Webmineral data
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
Wiberg, Egon, Nils Wiberg, and Arnold Frederick Holleman. Inorganic Chemistry. San Diego: Academic Press, 2001.
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.
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.

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[Mindat-1] Dimorphite mineral information and data Mindat.org

[Handbook-2] Handbook of Mineralogy

[3] Webmineral data

[4] 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

[Inorganic-5] Wiberg, Egon, Nils Wiberg, and Arnold Frederick Holleman. Inorganic Chemistry. San Diego: Academic Press, 2001.

[6] 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.

[7] 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.