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Formula: Sr2Al(PO4)2(OH)
Phosphate, brackebuschite supergroup,
strontium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.83 calculated
Hardness: 5
Colour: Colourless
Environments
Pegmatites
Hydrothermal environments
Localities
The type locality, the Palermo No. 1 Mine, Groton, Grafton County, New Hampshire, USA, is a complex
granite
pegmatite, with 159 valid mineral species reported by
August 2024.
A large corroded mass of triphylite was emplaced at the interface between
the quartz core and the intermediate zone of
quartz, perthite and
mica. The upper part of the mass consisted almost entirely of
ferric and manganic oxides and
remnant outlines of siderite crystals in vuggy cavities. The lower part
was extensively replaced by dense whitlockite-carbonate
apatite-siderite rock in which
open cavities up to 2 cm across occur.
About twenty hand specimens showing goedkenite were collected. It invariably occurs in close association with
palermoite (less so with quartz)
and crystallised later than that mineral. Single prisms of palermoite
frequently "spear" single crystals of goedkenite. The paragenesis is interpreted as a carbonate and calcium
replacement of earlier triphylite at the stage where the aqueous-rich
fluid separated from the rest liquid during consolidation of the core. In the process, Li1+ and metals of
the first transition series entered into solution. The triphylite
provided Li1+, Fe2+, Mn2+ and [PO4]3-, and the aqueous-rich fluid
provided Ca2+, Al3+, CO2 and subordinate amounts of Ba2+ and
Sr2+. Oxidation of some of the Fe2+ to form hydroxides along with the formation of
siderite led to local enrichment of Mn2+ relative to
F2+ at some later stage. If the conditions were sufficiently stagnant, minor cations such as
Ba2+ and Sr2+ would become concentrated whereas Ca2+ would be preferentially
sequestered in whitlockite and
apatite. At the final stage, the local fluid was sufficiently concentrated
in Sr2+ to allow a goedkenite replacement of goyazite and
palermoite.
In addition to the three new (in 1975) phosphate species foggite,
goedkenite and samuelsonite, associated minerals include
quartz, siderite,
scorzalite, goyazite,
palermoite, bjarebyite,
childrenite and arrojadite
(AM 60.957-964).
The goedkenite was originally found as small (less than 1 mm) colourless crystals growing epitaxially and
perpendicularly on palermoite crystals
(Mindat).
Goedkenite from the Palermo No 1 Mine -
Image
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