Millisite

millisite

fluorapatite

wardite

variscite

Images

Formula: NaCaAl₆(PO₄)₄(OH)₉.3H₂O
Hydrated phosphate containing hydroxyl, wardite group
Crystal System: Tetragonal
Specific gravity: 2.83 measured, 2.87 calculated
Hardness: 5½
Streak: White
Colour: White to light grey, colourless in transmitted light.
Environments:

Hydrothermal environments

Millisite is found in altered phosphate deposits.

Localities

At the Mount Deverell variscite deposit, Milgun Station, Western Australia, millisite is associated with wardite. The variscite deposits are hosted by marine sedimentary rocks (AJM 20.2.26).

The type locality is Clay Canyon, Fairfield, Oquirrh Mountains, Utah county, Utah, USA.
At the Little Green Monster Variscite Mine, Clay Canyon, Fairfield, Oquirrh Mountains, Utah county, Utah, USA, millisite is associated with carbonate-rich fluorapatite and wardite (Dana).

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