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Formula: (NH4)2Mg(SO4)2.6H2O
Hydrated sulphate, picromerite group, forms a series with
mohrite
Crystal System: Monoclinic
Specific gravity: 1.722 measured, 1.722 calculated
Hardness: 2
Streak: White
Colour: Colourless, yellowish-pink; colourless in transmitted light.
Luminescence: Not fluorescent under UV
Solubility: Water soluble, sharply astringent and saline taste
Environments
Geysers
Fumeroles
Coal seam fires
Boussingaultite occurs in geysers and in anthracite mine dump fires. It may originate as an alteration
(hydration) product of efremovite
(Mindat).
Localities
At the type locality, Travale, Montieri, Grosseto Province, Tuscany, Italy, boussingaultite occurs in
boric acid fumaroles
(Mindat).
At South Mountain, Santa Paula, Ventura county, California, USA, on the southern slopes of the mountain are two large
crevices in disturbed sandstone and chalky
shale, from which heated gas emanates continually; in these,
boussingaultite forms, as stalactites and encrustations at the openings
(AM 5.127-128)
At Mahanoy City, Schuylkill county, Pennsylvania, USA, boussingaultite occurred following a fire in a bank
of anthracite breaker refuse. A series of holes was drilled into the refuse to locate the fire. The hole around which
the boussingaultite was discovered was drilled until hot vapors were enountered at a depth of 158 feet. The
temperature at the bottom of this hole was 370oC. Limestone
dust in an aqueous suspension was poured down the hole to aid in extinguishing the fire. The dust was found, upon
excavation of the burning refuse, to have traveled to the outer limits of the fire and deposited as a chalk-like
mass from the holes in the hottest zone.
Pinkish crystals of boussingaultite were found, upon excavation of the burned refuse, filling cavities in the
refuse near the edges of the deposits of the limestone dust. Refuse
material was found cemented together by some of the crystals. The presence of unburned coal, which has an ignition
temperature of 470oC, indicates that the sample was not heated higher than this temperature, even though
the refuse reportedlyd burned to ashes. The boussingaultite evidently formed after the hot refuse cooled.
Boussingaultite crystallises, without decomposition, from an aqueous solution. The crystals varied in colour
from colourless to a yellowish-pink and were about 1 mm across
(AM 29.392-394).
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