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Formula: Ca3Al7.7Si3P4O23.5(OH)14.1.8H2O
Hydrated phosphate, perhamite group
Crystal System: Trigonal
Specific gravity: 2.64 measured, 2.53 calculated
Hardness: 5
Streak: White
Colour: Colourless, white, light brown, orange
Common impurities: Ti,Fe,Mg,Na,F
Environments
Localities
At the phosphate deposits of South Australia, perhamite is most often found as
pseudomorphs after other phosphate minerals,
such as fluellite, minyulite
and especially
wavellite
(AJM 17.1.24).
At the Moculta phosphate quarry, Angaston, Barossa Valley, Mount Lofty Ranges, South Australia, perhamite
occurs on a
matrix of apatite and quartz
(AM 91.1945).
At Tom's quarry, Kapunda, Mount Lofty ranges, South Australia, perhamite is associated with
fluellite, minyulite and
wavellite
(HOM).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, perhamite forms aggregates to 8 mm on
albite, quartz or
muscovite in miarolytic cavities in an albitised portion of the
pegmatite. Recent (2017)
finds indicate an unusual association of perhamite with pollucite
at the contact of lepidolite veins in
pollucite. The Emmons
pegmatite is an example of a highly evolved
boron-lithium-cesium-tantalum
enriched pegmatite
(R&M 94.6.513).
At the co-type localities, the Bell pit and the Dunton Gem Quarry, Newry, Oxford county, Maine, USA, perhamite
was originally found as late-stage mineralisation in granite
pegmatites; subsequently
it was found in oxidised zones of ore deposits (Mindat). Associated minerals include
siderite,
wardite, amblygonite,
eosphorite and sphalerite
in a vuggy amblygonite-rich
pegmatite zone
(MM 41.437-442, AM 63.794, HOM).
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