Triphylite

minerals

ferrisicklerite

lithiophilite

sillimanite

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Formula: LiFe2+(PO4)
Anhydrous normal phosphate, triphylite group, forms a series with lithiophilite. Epitaxial mineral - graftonite (Mindat).
Specific gravity: 3.42 to 3.58
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

Pegmatites

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 superficial, 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 The schist has been replaced by black tourmaline, muscovite and albite in a zone extending a few inches from the contact with the pegmatite; triphylite and its alteration products, garnet and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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