Avogadrite

(repeating unit)(K,Cs)BF₄IMA symbolAvg^[1]Strunz classification3.CA.10Crystal systemOrthorhombicCrystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)Space groupPnmaUnit cella = 8.6588, b = 5.48
c = 7.0299 [Å]; Z = 4IdentificationColorColorless to white, yellowish to reddishCrystal habitTabular to platy octagonal crystals, tiny crystals, elongateLusterVitreous, greasyDiaphaneityTranslucentSpecific gravity2.9Optical propertiesBiaxial (-)Refractive indexn_α = 1.3239, n_β = 1.3245, n_γ = 1.3247Birefringenceδ = 0.0012V angle75°(meas), 58° (calc)Other characteristicsBitter tasteReferences^[2]^[3]^[4]

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.

History

The 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

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

^ 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. {{cite journal}}: Cite journal requires |journal= (help)