Crandallite

phosphate

millisite

Formula: CaAl3(PO4)(PO3OH)(OH)6 hydrated phosphate containing hydroxyl
Specific gravity: 2.92
Hardness: 5
Streak: White
Colour: Yellow, white, gray; colourless in transmitted light.
Solubility: Soluble with difficulty in acids.
Environments:

Pegmatites
Sedimentary environments

Crandallite is a secondary mineral that occurs in iron-rich, silica-poor phosphate deposits and as an alteration product in pegmatites (Dana).

Alteration

Crandallite may be found as a pseudomorph after gordonite (Dana).

Common impurities: Sr and Ba substituting for Ca and Fe3+ for Al (Dana).

In the phosphate deposits of South Australia crandallite is found as a replacement of other phosphate minerals, notably wavellite, also apatite, fluellite and minyulite (AJM 17.1.14).

At the Bone Valley Formation, Florida, USA, crandallite is associated with clay, millisite and wavellite (Dana).

At the Brooklyn Mine, Utah, USA, crandlallite is associated with quartz and baryte (Dana).

At Fairfield, Utah, USA, crandallite is associated with millisite, wardite, variscite, gordonite, englishite, montgomeryite, overite, kolbeckite and apatite (Dana).

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