Avogadrite ((K,Cs)BF4) is a potassium-caesium tetrafluoroborate in the halide class. Avogadrite crystallizes in the orthorhombic system (space group Pnma) with cell parameters a 8.66 Å, b 5.48 Å and c Å 7.03.
| Avogadrite | |
|---|---|
 Ferruccite (white) on avogadrite (yellow-brownish), picture size: 5 mm | |
| General | |
| Category | Halide mineral |
| Formula (repeating unit) | (K,Cs)BF4 |
| IMA symbol | Avg[1] |
| Strunz classification | 3.CA.10 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnma |
| Unit cell | a = 8.6588, b = 5.48 c = 7.0299 [Å]; Z = 4 |
| Identification | |
| Color | Colorless to white, yellowish to reddish |
| Crystal habit | Tabular to platy octagonal crystals, tiny crystals, elongate |
| Luster | Vitreous, greasy |
| Diaphaneity | Translucent |
| Specific gravity | 2.9 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.3239, nβ = 1.3245, nγ = 1.3247 |
| Birefringence | δ = 0.001 |
| 2V angle | 75°(meas), 58° (calc) |
| Other characteristics | Bitter taste |
| References | [2][3][4] |
History
editThe mineral was discovered by the Italian mineralogist Ferruccio Zambonini in 1926. He analyzed several samples from the volcanic fumaroles close to Mount Vesuvius and from the Lipari islands. In nature, it can only be found as a sublimation product around volcanic fumaroles.[2] He named it after the Italian scientist Amedeo Avogadro (1776–1856).[5]
Bibliography
edit- Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 97-98.
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 "Handbook of Mineralogy: Avogadrite" (PDF). The Mineralogical Society of America. Archived from the original (PDF) on 2012-02-18. Retrieved 2010-01-09.
- ^ Avogadrite on Mindat.org
- ^ Avogadrite data on Webmin
- ^ Zambonini, Ferruccio (1926). "Sulla presenza, tra i prodotti dell'attuale attività del Vesuvio, di una varietà cesifera del fluoborato di potassio, (On the presence, among the products of Vesuvius, of a caesium-bearing variety of potassium fluoborate), Rend. Accad. Lincei". 6 (III): 644–649.
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