Westerveldite from Igdlúnguaq, Ilímaussaq Alkaline Massif, South Greenland1

I. S. Oen, E. A. J. Burke and C. Kieft
Geologisch Instituut der Universiteit van Amsterdam
Instituut voor Aardwetenschappen der Vrije Universiteit
Nederlandse Organisatie voor Zuiver Wetenschappelijk Onderzoek (ZWO)
1Contribution to the mineralogy of Ilímaussaq no. 44.

Summary: Microprobe and X-ray investigation of a mineral occurring with breithauptite, nickeline, and other arsenides in the naujaite at Igdlúnguaq, Ilímaussaq alkaline massif, S. Greenland, shows that this mineral, which was formerly misidentified as ‘maucherite’, is a westerveldite (Fe0·85Ni0·15)As, of much iron-richer composition than the nickeloan westerveldites from the only two other known occurrences of this mineral. Westerveldite from Igdlúnguaq was presumably formed by reaction of nickeline with iron-rich solutions under conditions of reheating at temperatures of about 450° C and under partial pressures of arsenic below those necessary to stabilize nickeline. Sulphur-bearing löllingite occurs as exsolution blades in the westerveldite. Iron-rich nickeline, up to a composition (Ni0·82Fe0·18)As0·95Sb0·05, was presumably formed by recrystallization of nickeline in the transition stage just before this mineral became unstable and was replaced by westerveldite.

Mineralogical Magazine; March 1977 v. 41; no. 317; p. 77-83; DOI: 10.1180/minmag.1977.041.317.12
© 1977, The Mineralogical Society
Mineralogical Society (www.minersoc.org)