Paravauxite

paravauxite

wavellite

crandallite

sigloite

Images

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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