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]
| Dimorphite | |
|---|---|
| General | |
| Category | Sulfide mineral |
| Formula (repeating unit) | As4S3 |
| IMA symbol | Dim[1] |
| 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 | [2][3][4] |
Properties and applications
editDimorphite 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
edit- ^ 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.
- ^ a b Dimorphite mineral information and data Mindat.org
- ^ a b 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
- ^ a b 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.