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Formula: (NH4)BF4
Fluoride, boron-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 1.89 measured, 1.9 calculated
Hardness: 1
Streak: White
Colour: Colourless
Solubility:
Common impurities: K,Na
Environments
Barberiite is formed by fumarolic activity, stable only at ground temperatures between 200oC and
600oC; it decomposes in humid air
(Mindat).
Localities
The type locality is La Fossa crater, Vulcano Island, Lipari, Eolie Islands, Messina Province, Sicily, Italy. The Fossa
volcano, for which documentation is available dating back to about 500 BC, is characterised by eruptions, generally
lasting a few years, interspaced by a few decades of calm, with intensive fumarolic activity. The last eruption began at
the Fossa crater in 1888 and ended in 1890; since then the volcano has remained in a fumarolic stage.
In 1987, when the maximum temperature of the fumaroles was below 400oC,
sulphur, salammoniac, and
sassolite were the only phases present in the fumarolic area. Since 1990,
when the maximum temperature of the hottest fumarole increased to 607oC,
bismuthinite, cannizzarite,
galenobismutite and
sphalerite have been collected, in addition to the minerals mentioned above.
In 1992 barberiite was also collected. Other associated minerals include
malladrite and realgar. The ground
temperature where the barberiite was collected ranged from 200oC to 600oC.
Barberiite occurs as globular aggregates to 2 mm in size admixed with
sulphur; salammoniac (where the
temperature of the ground is below 300oC), malladrite and
realgar also are admixed. Very thin crystals of barberiite, about 1
micron in thickness, range from about 50 to 300 microns in length.
Tetrafluoroborate ions BF-4 can be formed only in a strongly acid solution containing more F than
B. Barberiite can be formed by the reaction between the colourless toxic gas boron trifluoride BF3 and
colourless solid ammonium fluoride NH4F. Barberiite in the sampling area reacts with hydrochloric acid
present in fumarolic fluids to form salammoniac NH4Cl, boron trifluoride BF3, and hydrofluoric
acid, HF
(AM 79.381-384).
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