GALILEIITE - A NEW METEORITIC PHOSPHATE MINERAL

A new mineral named galileiite, NaFe4(PO4)(3), has been found within t roilite nodules in iron meteorites of the IIIA and IIIB groups. The mi neral is optically positive (omega = 1.72, epsilon = 1.75), colorless in transmitted light and pale amber in reflected light. Grains of gali leiite are very small, generally 10 mu m or less; rarely, grains are u p to 30 mu m. It is associated with Ca-free graftonite (or Ca-free sar copside), chromite and, occasionally, schreibersite. Johnsomervilleite may occur within troilite nodules in the same meteorite as galileiite , but they have never been observed together in the same troilite nodu le. Because of the small sample size, single crystal x-ray work was no t successful; however, Gandolfi diffraction measurements were made. Th e three strongest diffraction peaks are 2.71 Angstrom, 3.01 Angstrom a nd 4.13 Angstrom. On the basis of its composition and similar diffract ion pattern, it is considered to be related to johnsomervilleite, fill owite and chladniite, all of which are rhombohedral and isostructural. Galileiite may also be rhombohedral, but that is yet to be demonstrat ed.