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Ralstonite: NaxMgxAl2-x(F,OH)6·(H2O) Cryolite: Na3AlF6
Comments: Massive cryolite with solution cavities lined with octahedral ralstonite crystals.
Location: Ivigtut, Greenland.
Scale: Picture size 0.5 cm.
© John Veevaert
Ralstonite: NaxMgxAl2-x(F,OH)6·(H2O) Gjerdingenite-Fe: K2[(H2O)2(Fe,Mn)][(Nb,Ti)4(Si4O12)2(O,OH)4]·4(H2O)
Comments: SEM photomicrograph of gjerdingenite-Fe. The mineral is dusted with tiny crystals of two phases. At high magnification, one of them is seen to form cubes and is probably ralstonite.
Location: Gjerdingselva, Lunner, Oppland, Oslo Region, Norway.
Scale: Crystal length 0.5 mm.
© Canadian Mineralogist