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Formula: Al(SO4)(OH).5H2O
Hydrated sulphate, paramorph of
rostite
Crystal System: Monoclinic
Specific gravity: 1.786 measured, 1.828 calculated
Hardness: 2½
Colour: Colourless
Solubility: Soluble in water
Environments
Localities
At Le Cetine di Cotorniano Mine, Chiusdino, Siena Province, Tuscany, Italy, jurbanite is associated
with rostite, gypsum,
pickeringite,
metavoltine,
ferrinatrite,
sideronatrite,
tamarugite and
uklonskovite
(HOM).
At the type locality, the San Manuel orebody, San Manuel Mine, San Manuel, San Manuel Mining District, Pinal
county, Arizona, USA, jurbanite occurs as small, clear, colourless crystals, with at least six other
phases in post-mine stalactitic material deposited on lagging and overhead pipes. Other identified phases
include epsomite,
hexahydrite,
pickeringite and
starkeyite. One additional phase, a white, fluffy, powdery
mineral, was not identified and apparently represents at least one other species, although it may be a mixture
of more than one phase.
Jurbanite is found in intimate association with the unidentified fluffy mineral as isolated crystals
and as clumps of crystals. The original material, which apparently formed by precipitation from mine water at
about 27oC and 100% relative humidity, was probably dominantly
epsomite and the precursor to the fluffy mineral, together with
minor pickeringite and jurbanite. Dehydration then
apparently produced hexahydrite and
starkeyite from the
epsomite, and the fluffy material from its precursor. It is not
certain if jurbanite and pickeringite were original
precipitates or the products of the decomposition of original phases; however both occur as clear crystals
and an origin as primary precipitates may thus be
favoured. Jurbanite shows no sign of decomposition under the normal low humidity conditions prevailing
in the southwestern desert
(AM 61.1-4).
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