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Formula: LiFe2+(PO4)
Anhydrous normal phosphate, triphylite group, forms a series with
lithiophilite.
Epitaxial mineral - graftonite (Mindat).
Crystal System: Orthorhombic
Specific gravity: 3.42 to 3.58 measured, 3.562 calculated
Hardness: 4
Streak: Colourless to greyish white
Colour: Brown-green, light green-grey, may appear blue-grey; colourless to pale yellow in transmitted light.
Solubility: Soluble in acids.
Common impurities: Mn,Mg,Ca
Environments
Triphylite is a lithium-bearing mineral, and the most abundant
primary phosphate
in granite pegmatites (HOM, Dana). Associated minerals include
ferrisicklerite, heterosite,
alluaudite, albite,
muscovite and quartz
(HOM, Mindat).
At the type locality, the Hühnerkobel Mine, Zwiesel, Bavaria, Germany, triphylite occurs in a
granite pegmatite embedded in
quartz and
associated with beryl, tantalite and
tourmaline (HOM, Mindat).
At the Chickering mine, Cheshire county, New Hampshire, USA, triphylitee is a common
primary phosphate, and much of it has been attacked by
hydrothermal solutions. It has frequently been totally altered to
ferrisicklerite,
heterosite, siderite, and a suite of
secondary phosphates. Occasionally the alteration is only
uperficial,
leaving an unaltered core (R&M 90.5.421).
At the Center Strafford pegmatite, Strafford county, New Hampshire, USA, the paragenetic sequence, from earliest to
latest, is
microcline, muscovite,
tourmaline, quartz,
beryl, triphylite, graftonite,
manganapatite, albite,
amblygonite, rhodochrosite,
fairfieldite, microcline,
quartz (again), columbite,
muscovite (again), garnet,
löllingite, cassiterite,
autunite, vivianite,
eosphorite, heterosite and possible
ferrisicklerite (AM 23.811).
At the Smith mine, Newport, Sullivan county, New Hampshite, USA, triphylite occurs in a quartz -
albite pegmatite. The rock immediately surrounding the pegmatite is a
schist composed essentially of quartz,
muscovite and biotite. Minor constituents are
sillimanite, staurolite,
garnet, albite variety oligoclase,
apatite, chlorite,
magnetite and zircon. Locally, however,
sillimanite or staurolite constitute a
large proportion of the schist. The schist
has been replaced by black tourmaline, muscovite
and albite in a zone extending a few inches from the contact with the pegmatite; triphylite
and its alteration products, garnet and biotite,
occur only locally. Vivianite is a common and uniformly distributed alteration product
of triphylite, intimately distributed within it (AM 28.90-98).
Alteration
Triphylite is altered by meteoric and hydrothermal solutions with ease, forming
ferrisicklerite with leaching of lithium. Alteration is usually accompanied by
the formation of secondary iron phosphates such as
strengite, phosphosiderite,
dufrénite, frondelite,
rockbridgeite and vivianite (Dana).
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