Anhydrous normal phosphate, alluaudite group and forms a series with alluaudite
Specific gravity: 3.4 to 3.5
Hardness: 5 to 5½
Colour: Straw-yellow to brownish yellow, green, greenish black; yellow to yellow-green in transmitted light
Solubility: Soluble in acids
Ferroalluaudite occurs in zoned granite pegmatites and in phosphatic nodules. Associated
minerals include triphylite, barbosalite,
ferrisicklerite and apatite
The type locality is Chanteloube, Razès, Bellac, Haute-Vienne, Nouvelle-Aquitaine, France.
At the Palermo No. 1 Mine, Groton, Grafton county, New Hampshire, USA, in a pegmatite, crystals of ferroalluauditemore or less replaced by ludlamite are found along one side of a pod, associated with arrojadite embedded in siderite, ludlamite and vivianite masses, which are within quartz-mica-perthite (a variety of feldspar) at the core of the pegmatite (Dana).
Ferroalluaudite occurs as an alteration product of varulite and arrojadite-(KFe), and itself alters to heterosite and purpurite (Mindat).
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