Lithiophilite

Lithiophilite is a mineral containing the element lithium. It is lithium manganese(II) phosphate with formula: LiMnPO4. It occurs in pegmatites often associated with triphylite, the iron end member in a solid solution series. The mineral with intermediate composition is known as sicklerite (Li(Mn,Fe)PO4). The name lithiophilite is derived from the Greek philos (φιλός) "friend," as lithiophilite is usually found with lithium.[2]

Lithiophilite
General
CategoryPhosphate minerals
Formula
(repeating unit)		LiMnPO4
Strunz classification8.AB.10
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPmnb (if holohedral)
Identification
ColorClove-brown, yellowish brown, honey-yellow, salmon-pink, blue-gray, gray
Crystal habitPrismatic – crystals shaped like slender prisms, stout prismatic, large single crystals, massive, oriented overgrowths
TwinningRare contact twins on {130}
Cleavage[100] perfect, [110] and [011] poor
Fractureuneven to conchoidal
Mohs scale hardness4–5
LusterVitreous to subresinous
StreakWhite to grayish white
DiaphaneityTransparent to translucent
Specific gravity3.445–3.50
Optical propertiesBiaxial (+), 2V = 65°
Refractive indexnα=1.669, nβ=1.673, nγ=1.682
Birefringenceδ =0.0130
PleochroismNone to weak
References[1][2][3]

Lithiophylite is a resinous reddish to yellowish brown mineral crystallizing in the orthorhombic system often as slender prisms. It is usually associated with lepidolite, beryl, quartz, albite, amblygonite, and spodumene of pegmatitic origin. It rather readily weathers to a variety of secondary manganese phosphates and oxides. It is a late-stage mineral in some complex granite pegmatites.[3] Members of the triphylite-lithiophilite series readily alter to secondary minerals.

The type locality is the Branchville Quarry, Branchville, Fairfield County, Connecticut where it was first reported in 1878.[2] The largest documented single crystal of lithiophilite was found in New Hampshire, US, measured 2.44×1.83×1.22 m3 and weighed ~20 tonnes.[4]

The synthetic form of triphylite, lithium iron phosphate, is a promising material for the production of lithium-ion batteries.

References
  1. Lithiophilite at WebMineral
  2. Lithiophilite at Mindat.org
  3. Lithiophilite in Handbook of Mineralogy
  4. P. C. Rickwood (1981). "The largest crystals" (PDF). American Mineralogist. 66: 885–907.

Bibliography
  • Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 665-669.
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