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Formula: Ca4(H2O)4[B4O4(OH)6]4(H2O)15
Tetraborate
Crystal System: Orthorhombic
Specific gravity: 1.77 measured, 1.775 calculated
Hardness: 2
Streak: White
Colour: Colourless
Luminescence: Not fluorescent under short wave or long wave UV
Solubility: Dissolves slowly in warm water. Soluble in hydrochloric acid, and the solution colours a flame yellowish
green, as is typical of boron-bearing minerals.
Environments
Sedimentary environments
Evaporite deposits
Alfredstelznerite was approved in 2007 but to date (December 2024) it has been reported only from the type
locality.
Localities
At the type locality, the Santa Rosa mine, Sijes, Susques Department, Jujuy Province, Argentina, alfredstelznerite
was found as a white radial aggregate covering a cavity in mudstone. The
Santa Rosa mine is a Tertiary (66 to 2.6 million years ago) playa-lake (dry lake bed)
borate deposit that consists of many beds of
colemanite and hydroboracite
intercalated in a folded playa-lake sedimentary sequence dominated by
mudstones, siltstones,
sandstones, tuffs and
evaporites. The mine is an open pit quarry that exhibits several decimetre-thick beds containing
colemanite (dominant) and
hydroboracite (subordinate). In addition to the mined
borates, ulexite and
inyoite are abundant, and
meyerhofferite, nobleite,
gowerite and inderborite are rare;
gypsum and anhydrite are common
minerals, whereas orpiment and realgar
are very rare. Inderite is also present in small nodules of prismatic crystals.
Alfredstelznerite occurs as white sprays of acicular crystals in a cavity of fractured
mudstone. It is not intimately associated with other
borates in the type specimen. The mineral was found immediately after the rainy
season and it is of secondary origin. The individual crystals are
colourless and transparent, the aggregates are white, and partly dehydrated crystals are translucent. The crystals are
elongate, up to 5 mm long and 30 microns wide
(CM 48.123-128).
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