Avogadrite

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Avogadrite
Ferruccite, Avogadrite - Vesuvius, Italia.jpg
Ferruccite (white) on avogadrite (yellow-brownish), picture size: 5 mm
General
Category Halide mineral
Formula
(repeating unit)
(K,Cs)BF4
Strunz classification 03.CA.10
Crystal system Orthorhombic
Unit cell a = 8.6588 Å, b = 5.48 Å, c = 7.0299 Å; Z=4
Identification
Color Colorless to white, yellowish to reddish
Crystal habit Tabular to platy octagonal crystals
Crystal symmetry Orthorhombic dipyramidal
H-M symbol: (2/m 2/m 2/m)
Space group: P nma
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)
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. As a result, 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.