Millisite

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

Hydrothermal environments

Millisite is found in altered phosphate deposits. At the type locality, the Little Green Monster Mine, Utah, USA, it is associated with dehrnite, lewistonite and wardite.