| dimorphite | |
|---|---|
| General | |
| Category | Mineral |
| Formula (repeating unit) | As4S3 |
| Crystal system | orthrhombic dipyramidal |
| Identification | |
| Formula mass | 395.88 g/mol |
| Color | orange-yellow |
| Cleavage | none |
| Fracture | brittle |
| Mohs scale hardness | 1.5 (between talc and gypsum) |
| Luster | adamantine |
| Streak | yellow |
| Diaphaneity | transparent |
| Density | 3.59 g/cm3 (avg) |
| Optical properties | biaxial |
| Dispersion | strong |
| Ultraviolet fluorescence | none |
| Other characteristics | burns 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
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).[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.
External Links
edit- Image of dimorphite sample (image available freely for educational use only) here.
References
edit- ^ "Dimorphite: Dimorphite mineral information and data". Mindat.org - the mineral and locality database. Retrieved 2009-03-10.
- ^ 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) - ^ David Barthelmy. "Dimorphite Mineral Data". Mineralogy Database. Retrieved 2009-03-10.
- ^ a b c 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 Soldi. B., 197 (1): 61–64, 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, doi:10.1016/S0040-6090(99)00707-5