Images
Formula: Mn2+5(PO3OH)2(PO4)2.4H2O
Hydrated acid phosphate, hureaulite group,
manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.15 to 3.20 measured, 3.23 calculated
Hardness: 5
Streak: Nearly white
Colour: Commonly pink to colourless, also red, orange, orange-red, reddish brown, yellowish brown, violet-rose, amber, grey
Solubility: Readily soluble in acids
Environments
Hureaulite is a late-stage secondary mineral formed by
alteration
of primary phosphates in complex
granite pegmatites, associated with
lithiophilite, triphylite,
heterosite, rockbridgeite,
cacoxenite, vivianite,
fairfieldite, dickinsonite,
eosphorite, stewartite,
strengite, phosphosiderite,
roscherite,
hydroxylapatite,
jahnsite and
triplite (HOM, Mindat).
Hureaulite is one of the more persistent low temperature transition metal phosphate hydrates derived from
hydrothermal attack of
triphylite-lithiophilite
crystals in granite
pegmatites. Hureaulite characteristically occurs
very late in the secondary phosphate paragenetic sequence
(AM 58.302-307).
Localities
At the type locality, Les Hureaux, Saint-Sylvestre, Haute-Vienne, Nouvelle-Aquitaine, France, hureaulite occurs
in a zone
of altered triphylite in a
granite pegmatite,
associated with rockbridgeite,
cacoxenite, and vivianite in
cavities
in heterosite (Dana, Mindat).
At the Stewart pegmatite, Pala, San Diego county, California, USA, hureaulite occurs with
sicklerite, phosphosiderite
and stewartite
in altered lithiophilite (Dana, AM 70.395-408).
At Branchville, Ridgefield, Fairfield county, and the Strickland Quarry, Portland, Middlesex county, Connecticut, USA,
hureaulite is a secondary mineral found with
fairfieldite, dickinsonite,
reddingite, and eosphorite
as hydrothermal alteration of lithiophilite (Dana).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, hureaulite is a common replacement of
rhodochrosite that is associated with
lithiophilite. Stewartite and
phosphoferrite are common associated minerals. The Emmons pegmatite is an example of
a highly evolved
boron-lithium-cesium-tantalum
enriched pegmatite
(R&M 94.6.508-509).
At the Palermo number 1 and Fletcher mines, Groton, Grafton county, New Hampshire, USA, hureaulite occurs in
weathered
triphylite with
phosphosiderite,
strengite and heterosite
(Dana).
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.
Hureaulite was discovered at the Keyes No. 1 mine as unusual orange masses to cabinet size and lustrous pink to
orange crystals to about 3 mm. Associated minerals include albite,
muscovite, triphylite,
rockbridgeite,
lazulite-scorzalite, pink
phosphosiderite crystals and
pyrite
(R&M 97.4.318).
Back to Minerals