Avogadrite

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Avogadrite
Ferruccite, Avogadrite - Vesuvius, Italia.jpg
Ferruccite (white) on avogadrite (yellow-brownish), picture size: 5 mm
General
CategoryHalide mineral
Formula
(repeating unit)
(K,Cs)BF4
Strunz classification3.CA.10
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma
Unit cella = 8.6588, b = 5.48
c = 7.0299 [Å]; Z = 4
Identification
ColorColorless to white, yellowish to reddish
Crystal habitTabular to platy octagonal crystals
LusterVitreous, greasy
DiaphaneityTranslucent
Specific gravity2.9
Optical propertiesBiaxial (-)
Refractive indexnα = 1.3239, nβ = 1.3245, nγ = 1.3247
Birefringenceδ = 0.001
2V angle75°(meas), 58° (calc)
References[1][2][3]

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[edit]

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 found as a sublimation product around volcanic fumaroles.[1] He named it after the Italian scientist Amedeo Avogadro (1776–1856).[4]

See also[edit]

References[edit]

  1. ^ a b "Handbook of Mineralogy: Avogadrite" (PDF). The Mineralogical Society of America. Retrieved 2010-01-09.
  2. ^ Avogadrite on Mindat.org
  3. ^ Avogadrite data on Webmin
  4. ^ 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.