Formula: CaAl3(PO4)(PO3OH)(OH)6
Hydrated phosphate containing hydroxyl, plumbogummite group, alunite supergroup
Crystal System: Trigonal
Specific gravity: 2.78 to 3.04 measured, 3.00 calculated
Hardness: 5
Streak: White
Colour: Yellow, white, grey; colourless in transmitted light.
Solubility: Soluble with difficulty in acids.
Common impurities: Sr and Ba substituting for Ca and Fe3+ for Al (Dana).

Sedimentary environments
Hydrothermal environments

Crandallite is a secondary mineral that occurs in iron-rich, silica-poor phosphate deposits and as an alteration product in pegmatites (Dana). It may be found as a pseudomorph after gordonite (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).

Crandallite from South Australia - Image

At the Milgun Variscite Mine, Milgun Station, Meekatharra Shire, Western Australia, crandallite is a common alteration product of variscite; it crystallised late in the paragenetic sequence, and occurs as inclusions in hydroxylapatite. The variscite deposits are hosted by marine sedimentary rocks (AJM 20.2.24).

At the Central Florida Phosphate Mining District, Polk county, Florida, USA, crandallite is associated with clay, millisite and wavellite (Dana).

Crandallite from the Central Florida Phosphate Mining District - Image

At the type locality, the Brooklyn Mine, Silver City, Tintic Mining District, Juab County, Utah, USA, crandallite occurs in a matrix of quartz - baryte where it fills cavities, either fully or partially. The cavities range in size from a few millimeters to 6 cm in diameter. The vein material also contains pyrite, enargite, galena and sphalerite. Tenorite crusts up to half a millimeter thick covered the crandallite in a few specimens.
Crandallite is white to pale grey, sometimes with shades of yellow and brown. So far (published March-April 2024), crandallite in the Tintic district has been seen only from the Brooklyn mine, although closely related minerals such as arsenocrandallite, arsenogoyazite and svanbergite have been found at other mines, so it is quite likely that crandallite may occur at these other mines as well (MinRec 55.2.197-198).

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

Crandallite from Fairfield - Image

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