Triphylite
Triphylite, LiFe2+(PO4): lithium iron phosphate, hardness 4 to 5, density 3.50 to 3.58, 4.40% lithium. Series with lithiophilite; alters to heterosite.
Triphylite is lithium iron phosphate, LiFe2+(PO4) on the IMA list (G, 1834, Germany): orthorhombic, bluish to greenish gray, hardness 4 to 5, density 3.50 to 3.58, with one perfect cleavage. The formula is 4.40% lithium by mass. It forms a series with lithiophilite and alters, losing lithium, to ferrisicklerite and heterosite.
In short
- The species. The Handbook of Mineralogy sheet calls triphylite “the most abundant primary phosphate in complex zoned granite pegmatites”: orthorhombic, crystals rare, commonly subhedral to 6.5 m, cleavable, compact or massive; cleavage {100} perfect; hardness 4 to 5; density 3.50 to 3.58; bluish gray to greenish gray, brownish to black where altered; streak white. The September 2026 IMA-CNMNC Master List writes LiFe2+(PO4), status G, 1834, Germany.
- The lithium figure and the 3.56 check. On standard atomic weights LiFe2+(PO4) weighs 157.75: 4.40% lithium, 35.40% iron, 19.63% phosphorus, or 9.47% Li2O. In the sheet’s cell (a 6.0285, b 10.3586, c 4.7031 Å, Z 4) it gives a density of 3.568, against the sheet’s calculated 3.562 and measured 3.50 to 3.58. A 20.00 g piece reads 14.29 to 14.41 g in water.
- The lithium-out chain. Three Handbook sheets describe what triphylite becomes. Ferrisicklerite forms “by late hydrothermal alteration or weathering of triphylite-lithiophilite”, as rims; heterosite replaces primary phosphates, “principally triphylite”. Worked per phosphorus, lithium falls from 1 (formula) to 0.39 (Varuträsk ferrisicklerite) to trace (Hill City heterosite), and the ferric share of the iron rises from 0% to 97.6% to 100%.
- Reading the crust. The chain changes what you see: bluish gray with a white streak (triphylite), yellowish brown to chocolate-brown with a brown streak (ferrisicklerite), deep rose to purple with a pale purple streak (heterosite). A dark rim on a grey phosphate is the sheets’ “brownish to black where altered”, not a different primary mineral.
- Series and neighbours. The sheet says triphylite forms a series with lithiophilite, the manganese member; triphylite vs lithiophilite covers how far a hand specimen can be placed. The order of the pegmatite phosphates is read on what is mineral paragenesis; huréaulite, eosphorite and childrenite are among the later phosphates of the same pegmatites.
| Mineral | Formula: Handbook; IMA | Occurrence as printed | Analysis used | Li per P | Fe3+ share of Fe | Colour as printed | Streak | Hardness | D(meas.) | 20.00 g in water |
|---|---|---|---|---|---|---|---|---|---|---|
| Triphylite | Li(Fe2+,Mn2+)PO4; LiFe2+(PO4) | The most abundant primary phosphate in complex zoned granite pegmatites | (1) “Central Asia”, Russia | 0.88 (formula 1) | 3.1% (formula 0%) | Bluish gray to greenish gray; brownish to black where altered | White to grayish white | 4–5 | 3.50–3.58 | 14.29–14.41 g |
| Ferrisicklerite | Li(Fe3+,Mn2+)PO4; no IMA row | Late hydrothermal alteration or weathering of triphylite-lithiophilite; rims | (1) Varuträsk, Sweden | 0.39 | 97.6% | Colorless, yellowish brown to dark chocolate-brown | Pale yellowish brown, brown, reddish brown | ~4 | 3.2–3.4 | 13.75–14.12 g |
| Heterosite | (Fe3+,Mn3+)PO4; Fe3+(PO4) | Oxidized zone; replacing primary phosphates, principally triphylite | (1) Hill City, South Dakota | trace | 100% | Deep rose to purple, black | Pale purple | 4–4.5 | 3.40 | 14.12 g |
What is triphylite? The pegmatite lithium iron phosphate
Triphylite is the iron end of the lithium phosphate series with lithiophilite, and its sheet calls it the most abundant primary phosphate of complex zoned granite pegmatites. The Handbook of Mineralogy triphylite sheet gives point group 2/m 2/m 2/m, space group Pmnb, a 6.0285, b 10.3586, c 4.7031 Å, Z 4. Crystals are rare, typically prismatic with large {011}, {100}, {010}, {021} and {120}; the usual material is subhedral, to 6.5 m, cleavable, compact or massive. Its associates are ferrisicklerite, heterosite, alluaudite and many other Fe–Mn phosphates and oxides.
Physical and optical properties. Cleavage {100} perfect, {010} imperfect, {011} interrupted; fracture uneven to subconchoidal; hardness 4 to 5; measured density 3.50 to 3.58, calculated 3.562. Bluish gray to greenish gray, brownish to black where altered; streak white to grayish white; lustre vitreous to subresinous; transparent to translucent. Biaxial (+), α 1.675 to 1.694, β 1.684 to 1.695, γ 1.685 to 1.700, 2V 0° to 55°, dispersion r < v, strong. The sheet prints no luminescence: a ligature-aware search finds the fluorescence lines on hemimorphite and willemite, the positive controls, and nothing on triphylite. How to read a break is on cleavage or fracture.
Name. The sheet derives it from the Greek for threefold and family, “as it contains three cations”. The IMA list gives 1834 and Germany, first reference Journal für Praktische Chemie 3 (1834). The sheet marks no type locality and names no type material; what the term means on a label is on what is a type locality.
Triphylite formula and lithium content: the 3.56 check
The IMA formula is the iron end member; the Handbook writes the series. The IMA list writes LiFe2+(PO4). The Handbook writes Li(Fe2+,Mn2+)PO4, and its ideal column (2) is Li(Fe,Mn)PO4 with Mn:Fe = 1:1: P2O5 45.11, FeO 22.84, MnO 22.55, Li2O 9.50. Worked on standard atomic weights the 1:1 composition gives 45.12, 22.84, 22.55 and 9.50. The iron end member gives P2O5 44.99, FeO 45.54 and Li2O 9.47.
Worked. LiFe2+(PO4) weighs 157.75: 4.40% lithium, 35.40% iron, 19.63% phosphorus. The sheet’s cell has a volume of 293.69 Å3; with Z 4 the end member gives a density of 3.568, and the 1:1 composition 3.558, either side of the sheet’s calculated 3.562. The measured range, 3.50 to 3.58, means a 20.00 g piece reads 14.29 to 14.41 g in water; the method is on how to measure specific gravity at home.
The analysed triphylite. The sheet’s column (1), from “Central Asia”, Russia, gives P2O5 44.76, FeO 30.05, MnO 12.40, Fe2O3 1.07, MgO 0.72, CaO 0.34, Li2O 8.33, H2O 0.25 and 1.55 insoluble. Per phosphorus: Fe2+ 0.66, Mn 0.28, Fe3+ 0.02, Mg 0.03, Ca 0.01 and Li 0.88, short of the formula’s 1. Iron is 71.2% of iron plus manganese, on the triphylite side of the series; triphylite vs lithiophilite sets that figure against the lithiophilite analyses.
What does triphylite alter to? The lithium-out chain
On the sheets, triphylite loses lithium as its iron oxidises, through ferrisicklerite to heterosite. The ferrisicklerite sheet says it forms “by late hydrothermal alteration or weathering of triphylite-lithiophilite in complex zoned granite pegmatites”, as rims around crystals and masses of triphylite-lithiophilite. The heterosite sheet calls heterosite “a secondary mineral in the oxidized zone of complex granite pegmatites, replacing primary phosphate minerals, principally triphylite”. The September 2026 IMA list has a row for heterosite, Fe3+(PO4), and none for ferrisicklerite or sicklerite: a script finds no line containing “icklerite”.
The swap, worked. In LiFe2+(PO4) the cations carry +3 against the phosphate’s −3. Take a lithium out and one iron must go from Fe2+ to Fe3+ to keep the balance; take all of it out and the result is Fe3+(PO4), 150.81 per formula against 157.75, the 4.40% that was lithium. The Varuträsk ferrisicklerite analysis on its sheet works out at Li 0.39, Fe3+ 0.54 and Mn 0.43 per phosphorus, a cation charge of 3.02. The Hill City heterosite analysis records lithium as a trace.
What it looks like. Colour and streak move with the chemistry: bluish to greenish gray with a white to grayish white streak, then yellowish brown to dark chocolate-brown with a brown streak, then deep rose to purple with a pale purple streak. Density falls from 3.50–3.58 to 3.2–3.4 and 3.40. The manganese side of the series runs the same way, lithiophilite through sicklerite to purpurite, by those sheets’ wording; triphylite vs lithiophilite says why a purple crust does not tell the two apart. The later phosphates that follow, including huréaulite, strengite and rockbridgeite, are read in order on what is mineral paragenesis.
Where is triphylite found? The sheet’s localities
The sheet says triphylite occurs at numerous localities and lists a selection. In Germany, Hühnerkobel, near Zwiesel, and Hagendorf, Bavaria. Sukula and Tammela, Finland. Varuträsk, Norrö and Skrumpetorp, Sweden. The La Vilate quarry, near Chanteloube, and Huréaux, Haute-Vienne, France. Dolni Borí, near Velké Meziříčí, Czech Republic. The Sapucaia pegmatite mine, about 50 km east-southeast of Governador Valadares, Minas Gerais, Brazil. In the USA, large crystals from the G.E. Smith quarry, Newport, and the Palermo #1 mine, near North Groton, New Hampshire; Newry and other places in Maine; the Dan Patch, Big Chief and Hesnard mines near Keystone, and the Bull Moose and Tip Top mines near Custer, South Dakota; the White Picacho district, Arizona. Point de Bois, Manitoba, Canada. The sheet names no British locality.
As a gem. The International Gem Society triphylite article describes facetable triphylite from Brazil, cut stones up to two carats, with orangish brown and green pleochroism and, in some, a slight colour change. The Handbook says nothing on cutting. No fetched USGS or BGS text gives triphylite a use, and this page states none.
Lithium relatives. A regex over the September 2026 IMA list for rows written as one alkali, one other metal and one phosphate finds seven: with lithium, triphylite (Fe2+), lithiophilite (Mn2+) and simferite (Mg); with sodium, karenwebberite (Fe2+), natrophilite (Mn2+), beryllonite (Be) and buchwaldite (Ca). The lithium silicates are on spodumene, petalite and lepidolite. Another pegmatite phosphate, sodium and aluminium rather than lithium and iron, is brazilianite. The reference section continues at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.