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Formula: Al(PO4).2H2O
Hydrated normal phosphate, metavariscite group, the monoclinic paramorph of
orthorhombic variscite
Crystal System: Monoclinic
Specific gravity: 2.51 to 2.54 measured, 2.53 calculated
Hardness: 3½
Streak: White
Colour: Light green; colourless in transmitted light
Environments:
Metavariscite occurs commonly as a product of weathering phosphatic rocks; it may form as concretions by the
phosphatisation of kaolin during weathering, and it is probably a reaction product
of phosphate fertiliser in acid soil
(HOM).
Common associates include fluellite,
montgomeryite and variscite
(Mindat).
Localities
At the Milgun Variscite Mine, Milgun Station, Meekatharra Shire, Western Australia, veins of "variscite" are commonly a
mixture of variscite and metavariscite. The veins may be altered and
replaced by secondary minerals including
montgomeryite, hydroxylapatite,
strengite and leucophosphite.
Variscite/metavariscite also forms
pseudomorphs after pyrite
(AJM 20.2.31-32).
At the Woodlands variscite gold occurrence, Woodlands Station, Meekatharra Shire, Western Australia,
variscite/metavariscite occurs intergrown with extremely fine-grained
quartz
(AJM 14.1.28-30).
At Malpelo Island, San Andrés y Providencia Department, Colombia, metavariscite occurs in phosphatised
andesite
(Dana).
At the Gunheath China Clay Pit, Stenalees, Treverbyn, Cornwall, England, UK, variscite
is uncommon, typically occurring as spherulitic aggregates of virtually colourless crystals, many of which contain white powdery
cores up to 1 millimetre in diameter. The cores are composed of variscite along
with variable amounts of metavariscite. The composition of the cores is similar to that of the surrounding
variscite spherule, but additionally containing traces of K, Si and Fe.
Variscite and metavariscite typically occur on a matrix of
granite pegmatite or
coarse quartz-tourmaline vein material.
Cassiterite occurs in the matrix of several specimens,
wavellite is a common and intimate associate, and
turquoise occurs on variscite on one
specimen. Many crystals of metavariscite are enclosed by partial or complete brown transparent vitreous crusts to
0.1 mm thick of pure variscite, although the brown colour is unusual.
Wavellite occurs on one specimen as sprays of acicular crystals to 3 mm intimate with,
and often penetrating, variscite
(MM 60.4.671-672).
At the Candelaria Mining District, Esmeralda county, Nevada, USA, massive metavariscite occurs
with variscite
(Dana).
At the Argentum Mining Co. Mine, Candelaria Mining District, Mineral County, Nevada, USA,
whiteite-(CaMgMg) is a low temperature,
secondary mineral presumed to have formed as a result of hydrothermal
alteration. It is associated with crandallite,
fluorwavellite, montgomeryite and
variscite/metavariscite
(CM 54.1513-1523).
At the type locality, the Edison Bird mine, Utahlite Hill, Lucin Mining District, Box Elder county, Utah, USA,
metavariscite occurs as sedimentary phosphate mineralisation along fractures, associated with
variscite
(Mindat).
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