Hochleitner, Rupert; Fehr, K. T.
Isokite, CaMg [FIPO4], from Senhora de Assunção, Portugal: New find and new data.
In: Neues Jahrbuch fur Mineralogie, Abhandlungen, Vol. 182, No. 1: pp. 103-108
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Isokite, CaMg[FIPO4], from a newly discovered occurrence in the pegmatite of Senhora de Assunção, Portugal, is described. In contradiction to previous descriptions (DEANS et al. 1955, FISHER 1957, DEANS 1958) the newly found isokite does not form whitish earthy crusts but massive brownish or greyish masses and veins in contact to triplite. Paragenesis and age relations show that Assunção isokite grows at the expense of earlier formed triplite. The FTIR spectrum of isokite is presented for the first time (observed bands at 456, 475, 564, 594, 649, 952, 1005, 1039, 1075, 1124 cm-1), chemical and X-ray diffraction data are given (a = 6.527 ± 0.005 Å, b = 8.744 ± 0.005 Å, c = 7.501 ± 0.006 Å and β = 121.34 ± 0.009°) and the formation of isokite in pegmatites is discussed.