Images
Formula: (Fe3+0.67◻0.33)2(Fe3+)3(PO4)3(OH)4(H2O)
Hydrated phosphate, rockbridgeite group
Crystal System: Orthorhombic
Specific gravity: 3.33 measured, 3.42 calculated
Colour: Reddish brown
Ferrirockbridgeite is a relatively new mineral, approved in 2019.
Localities
At the type locality, the Palermo No. 1 Mine, Groton, Grafton County, New Hampshire, USA, the specimen now designated
as the holotype was found in the form of radial fibrous crusts and masses, derived from the alteration of
triphylite and including both ferrirockbridgeite and
rockbridgeite. A portion of this specimen comprised millimetre-sized
chips, composed of compact intergrowths of reddish-brown blade-like crystals, whose measured specific gravity is 3.33,
whereas the value calculated for the empirical formula is 3.42
(European Journal of Mineralogy: 31.3.585-594).
Back to Minerals