Ralstonite n. : A fluoride of alumina and soda occurring with the Greenland cryolite in octahedral crystals.

Example:


Taxonomy
Ralstonite, Minerals, H2O, Mineral Data, On/Off, gm, d3m, Discussion Group, crystallography, physical properties, optical properties, Electron Density, radioactivity, cryolite, Fabre Minerals, chemical composition, Locality, Ivigtut.

Defination from the web:
Ralstonite Gjerdingenite-Fe. 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. ...