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Formula: Ca2Fe3+3O2(PO4)3.3H2O
Hydrated phosphate, mitridatite group, forms a series with
arseniosiderite
Specific gravity: 3.25
Hardness: 2½
Streak: Pale green
Colour: Greenish-yellow, olive green, brownish-green, etc.
Solubility: Soluble in hot acids.
Environments:
Pegmatites
Sedimentary environments
Mitridatite is a common stain or crust on minerals near oxidising ferrous phosphate minerals, typically
triphylite or vivianite in
granite pegmatites; it is a component of cement or fossil replacements in some
ferruginous oolitic sediments, and it occurs in phosphatic soils. Associated minerals include
diadochite, triphylite,
vivianite, rockbridgeite,
heterosite, hureaulite,
fairfieldite, cyrilovite,
jahnsite, laueite,
collinsite, apatite,
strunzite and iron hydroxides (HOM, Mindat)
Localities
At the Moculta quarry, Angaston, Barossa Valley, Mount Lofty Ranges, South Australia, mitridatite is associated
with fluorapatite and
leucophosphite
(AJM 17.1.22).
At Tom's quarry, Kapunda, Mount Lofty Ranges, South Australia, mitridatite is found within the
natrodufrénite-leucophosphite-kapundaite
assemblage associated with fluorapatite and
leucophosphite, and rarely with
ushkovite
and xanthoxenite
(AJM 17.1.22).
At the Mount Deverell variscite deposit, Milgun Station, Western Australia,
mitridatite is a common weathering product of variscite, and the
second most abundant phosphate in the
deposit (variscite is the first). The
variscite
deposits are hosted by marine sedimentary rocks
(AJM 20.2.27).
At the co-type localities, Mount Mithridat and the Kerchenskoe deposit, both on the Kerch Peninsula, Crimea, Russia,
mitridatite occurs in oolitic sedimentary iron ores associated with
vivianite and
anapaite (Mindat).
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.
Mitridatite has been found as an olive-green coating on childrenite
crystals
(R&M 97.4.321).
Paragenesis
The sequence triphylite-ferrisicklerite-rockbridgeite-leucophosphite-hureaulite
+ laueite-mitridatite-bermanite-todorokite
appears repeatedly at the Tip Top, White Elephant and Linwood
pegmatites in the Black Hills, Custer county, South Dakota,
USA, at Hagendorf, Bavaria, Germany, at Palermo Number 1, New Hampshire, USA and at
the Sapucaia pegmatite, Brazil. At the White Elephant
pegmatite, mitridatite is a particularly persistent
phase at all stages of late crystallisation and occurs widely as stains coating the silicates surrounding
triphylite crystals at practically every
pegmatite where
triphylite occurs, suggesting that mitridatite is an important low
temperature phase
(AM 59.48-59).
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