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Formula: Fe2+Al2(PO4)2(OH)2.8H2O
Hydrated phosphate containing hydroxyl, laueite group, triclinic
paramorph of monoclinic
metavauxite
Crystal System: Triclinic
Specific gravity: 2.36 measured, 2.37 calculated
Hardness: 3
Streak: White
Colour: Colourless to pale greenish white
Environments
Pegmatites
Hydrothermal environments
Paravauxite is a rare mineral in hydrothermal tin veins and in complex
granitic
pegmatites (Mindat). Associated minerals include
vauxite, metavauxite and
wavellite
(Webmin).
Localities
At the type locality, the Siglo Veinte mine, Llallagua, Rafael Bustillo, Potosí, Bolivia, paravauxite occurs
as a later secondary phosphate in hydrothermal
tin veins. It almost always occurs as individual crystals to 2 cm perched on
wavellite encrusting quartz in
the tin veins and porphyry
breccia fragments; childrenite
has often been observed in association with the paravauxite on wavellite,
and paravauxite crystals have been found in vugs in wavellite. It has
been found on crusts of vauxite and as crystals perched on
metavauxite needles. Other associated minerals include
allophane, sigloite,
quartz and crandallite
(Min Rec 37.2.145, Mindat). Sigloite forms oxidation
pseudomorphs after paravauxite
(AM 47.1 to 8).
At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA,
paravauxite-laueite-group minerals occur as sprays and clusters of
thin bladed crystals
(R&M 90.5.420).
At the Keyes Mica Quarries, Orange, Grafton County, New Hampshire, USA, the
pegmatites are beryl-type
rare-element (RE) pegmatites.
The Number 1 mine exposed a pegmatite that shows the most
complex zonation and diverse mineralogy of any of the Keyes
pegmatites. Six zones are distinguished, as follows, proceeding
inward from the margins of the pegmatite:
(1) quartz-muscovite-plagioclase
border zone, 2.5 to 30.5 cm thick
(2) plagioclase-quartz-muscovite
wall zone, 0.3 to 2.4 metres thick
(3) plagioclase-quartz-perthite-biotite
outer intermediate zone, 0.3 to 5.2 metres thick, with lesser muscovite
(4) quartz-plagioclase-muscovite
middle intermediate zone, 15.2 to 61.0 cm thick
(5) perthite-quartz inner intermediate zone, 0.9 to 4.6 meters thick
(6) quartz core, 1.5 to 3.0 metres across
The inner and outer intermediate zones contained perthite crystals up to
1.2 meters in size that were altered to vuggy
albite-muscovite with
fluorapatite crystals. This unit presumably was the source of the
albite, muscovite,
fluorapatite, quartz and other
crystallised minerals found in pieces of vuggy albite
rock on the dumps next to the mine.
The middle intermediate zone produced sheet mica with accessory minerals including
tourmaline, graftonite,
triphylite, vivianite,
pyrite, pyrrhotite, and
beryl crystals to 30.5 cm long and 12.7 cm across.
Paravauxite has been identified as submillimeter beige crystals associated with
strunzite
(R&M 97.4.322).
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