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Formula: NaAl(PO4)F
Anhydrous phosphate containing halogen, tilasite group
Specific gravity: 3.126 to 3.29
Hardness: 4½
Streak: White
Colour: Colourless, light yellow, light green, almost white, colourless in transmitted light
Solubility: Readily soluble in hydrochloric and sulphuric acid
Environments
Lacroixite frequently occurs as grains and rods in the altered margins of amblygonite or
montebrasite embedded in a granite pegmatite matrix
(Mindat).
Localities
At the type locality, the Greifenstein Rocks, Ehrenfriedersdorf, Erzgebirgskreis, Saxony, Germany, lacroixite occurs in a
lithium-bearing granite pegmatite intimately mixed with
its alteration product viitaniemiite and associated with
muscovite, morinite,
ježekite, fluorapatite,
childrenite, roscherite,
feldspar, elbaite and
quartz
(HOM, Dana, Mindat).
At the Rusororo pegmatite, Gatumba, Ngororero District, Western Province, Rwanda, lacroixite occurs as an alteration product in a complex
granite pegmatite, associated with montebrasite,
scorzalite and berlinite
(HOM).
At the Strickland Quarry, Strickland pegmatite, Collins Hill, Portland, Middlesex county, Connecticut, USA, lacroixite is associated with
apatite, augelite and
brazilianite
(HOM).
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