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Formula: Ca2Fe2+(PO4)2.2H2O
Hydrated normal phosphate, fairfieldite group
Crystal System: Triclinic
Specific gravity: 3.15 to 3.16 measured
Hardness: 3½
Streak: White
Colour: White, pale grey white, creamy white
Environments
Pegmatites
Hydrothermal environments
Messelite occurs principally as a late stage hydrothermal alteration product in zoned complex
granite pegmatites.
Associated minerals include
triphylite, anapaite,
vivianite, ludlamite,
siderite, goyazite,
whitlockite, herderite,
amblygonite, eosphorite,
brazilianite, graftonite,
fairfieldite, phosphoferrite,
hureaulite and jahnsite group minerals
(HOM, Mindat).
Localities
At the type locality, the Messel mine, Messel, Darmstadt-Dieburg, Darmstadt, Hesse, Germany, messelite occurs in bituminous
clay associated with anapaite
(Mindat).
Messelite from the Messel Mine - Image
At the Prinz von Hessen Mine, Messel, Darmstadt-Dieburg, Darmstadt, Hesse, Germany, messelite occurs in the coal mine as a late hydrothermal
product rimmed with anapaite in a granite
pegmatite
(Dana).
Messelite from the Prinz von Hessen Mine -
Image
At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA, messelite-fairfieldite
is moderately common as masses of bladed crystals to 2 mm. They occur where triphylite has altered to
secondary phosphates, with ludlamite as a common
associate
(R&M 90.5.419)
At the Palermo No. 1 Mine, Groton, Grafton county, New Hampshire, USA, messelite occurs as a late hydrothermal mineral in the
pegmatite in two ways:
Firstly, as pale greenish white to greenish grey masses associated principally with siderite,
plagioclase and quartz, whilst other associated minerals
include goyazite, whitlockite,
herderite, amblygonite,
eosphorite, brazilianite and
sphalerite.
Secondly as almost pure white masses either deposited on crystals of ludlamite in veinlets cutting
triphylite, or embedded in veinlets or patches of granular material composed largely of
siderite, quartz and
plagioclase with minor amounts of amblygonite,
ludlamite, whitlockite and
sphalerite
(AM 40.828-833).
Messelite from the Palermo No. 1 Mine -
Image
At the Bull Moose Mine, Custer, Custer Mining District, Custer county, South Dakota, USA, messelite occurs with
hureaulite in the pegmatite
(Dana).
At the Tip Top Mine, Fourmile, Custer Mining District, Custer county, South Dakota, USA, messelite occurs in altered
triphylite in the pegmatite
(Dana).
Messelite from the Tip Top Mine -
Image
At Big Chief Mine, Glendale, Keystone Mining District, Pennington county, South Dakota, USA, messelite occurs in the
pegmatite as large
crystals with siderite and ludlamite
(Dana).
Dan Patch Mine, Keystone, Keystone Mining District, Pennington county, South Dakota, USA, messelite occurs with
triphylite
(Dana).
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