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Formula: Fe2+Al(PO4)(OH)2.H2O
Hydrated phosphate containing hydroxyl, forms a series with eosphorite
Crystal System: Orthorhombic
Specific gravity: 3.11 to 3.19 measured, 3.13 calculated
Hardness: 5
Streak: White
Colour: Yellowish brown, brown, clove-brown; colourless in transmitted light.
Solubility: Soluble in acids.
Common impurities: Ca,Mn
Environments:
Pegmatites
Hydrothermal environments
Childrenite occurs in some complex granite pegmatites; it is typically a low-temperature
hydrothermal alteration product of primary phosphate minerals (HOM). Associated
minerals include apatite, goethite,
siderite and tourmaline (Mindat).
At Tom's quarry, South Australia, childrenite lines cavities in variscite and
crandallite and forms an intergrowth with beryl
(AJM 17.1.14).
At Llallagua, Bolivia, childrenite is often found without associated species, but it also has been found encrusting
paravauxite, wavellite or
vivianite (MinRec 37.2.131).
At Greifenstein, Erzgebirge District, Saxony, Germany, childrenite is associated with zinnwaldite (a series between
siderophyllite and polylithionite),
tourmaline, apatite and
kaolinite (HOM).
At the Trepča Stan Terg mine, Kosovska Mitrovica, Kosovo, childrenite occurs with its alteration product,
crandallite, associated with siderite,
ankerite, rhodochrosite,
quartz and sometimes vivianite.
Some childrenite crystals
have inclusions of boulangerite (MinRec 38.4.281).
At St Austell, Cornwall, England, UK, childrenite occurs with zinnwaldite,
tourmaline and apatite (Dana).
At the type locality, Tavistock, Devon, England, UK, childrenite occurs in low temperature hydrothermal veins, associated with
siderite, quartz,
pyrite and fluorapatite
(Mindat, HOM, Dana)
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, childrenite typically occurs where
montebrasite and
triphylite-lithiophilite are in
close proximity. Aluminium from the montebrasite is essential in the formation
of childrenite-eosphorite minerals. The Emmons pegmatite is an example of a
highly evolved
boron-lithium-cesium-tantalum
enriched pegmatite
(R&M 94.6.506).
At the Chickering mine, Walpole, Cheshire county, New Hampshire, USA, childrenite is one of the commonest secondary phosphate
minerals. It is found in late-stage, triphylite replacement cavities, associated with
siderite, apatite,
strunzite, quartz, and
albite (R&M 90.5.414).
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.
Childrenite forms dark brown crystals to several millimeters long, mostly coated by olive-green
mitridatite. Associated minerals include tabular white
apatite crystals and probable goyazite
crystals
(R&M 97.4.314).
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