Formula: Al(PO4)
Anhydrous normal phosphate
Specific gravity: 2.64 to 2.66
Hardness: 6½
Streak: White
Colour: Colourless, greyish or pale pink; colourless in transmitted light.
Solubility: Readily soluble in alkalies; virtually insoluble in cold acids.
Common impurities: Fe,Si

Metamorphic environments
Hydrothermal environments

Berlinite is a rare high-temperature hydrothermal or metasomatic mineral. Often found in caves after guano fires (Webmin, HOM).
It is isostructural with quartz, which is a tectosilicate (framework silicate). Berlinite inverts at 583° to a paramorph isotypic with β-SiO2 (Mindat)
In granite pegmatites associated minerals include augelite, attakolite, kyanite, pyrophyllite, scorzalite, lazulite, gatumbaite, burangaite, amblygonite, phosphosiderite, purpurite, apatite, muscovite, quartz and hematite (HOM).

At Paddy's River mine, Australia, berlinite is associated with alunite, aragonite, apatite variety collophane, crandallite, francoanellite, gypsum, huntite, hydromagnesite, leucophosphite, nesquehonite, niter and nitrocalcite (HOM).

At the type locality, the Västanå Iron Mine, Näsum, Bromölla, Skåne County, Sweden, berlinite is associated with augelite and attakolite (Mindat).

augelite to berlinite, corundum and H2O
2Al2(PO4)(OH)3 to 2Al(PO4) + Al2O3 + 3H2O
(AM 64.1175-1183)

berlinite and H2O to trolleite and phosphoric acid
4Al(PO4) + 3H2O to Al4(PO4)3(OH)3 + H3PO4
(AM 64.1175-1183)

trolleite to augelite and berlinite
Al4(PO4)3(OH)3 to Al2(PO4)(OH)3 + 2Al(PO4)
(AM 64.1175-1183)

trolleite to berlinite, corundum and H2O
2Al4(PO4)3(OH)3 to 6Al(PO4) + Al2O3 + 3H2O
(AM 64.1175-1183)

Back to Minerals