Occurrences of Sinoite, Si₂N₂O, in Meteorites

Abstract

THE recent discovery of the new mineral sinoite, Si₂N₂O, in the Jajh deh Kot Lalu enstatite chondrite^1–3 prompted a systematic search for this compound in the other fourteen enstatite chondrites at present known to exist in the world's meteorite collections (Abee, AdhiKot, Atlanta, Bethune, Blithfield, Daniel's Kuil, Hvittis, Indarch, Khairpur, Kota-Kota, Pillistfer, St. Marks, Saint-Sauveur, Ufana). Of these fourteen enstatite chondrites, three were found to contain sinoite. These three are the Hvittis, Ufana and Pillistfer stones. The appearance of the mineral in these meteorites is very similar to its appearance in the Jajh deh Kot Lalu enstatite chondrite. In reflected light, the crystals are distinctly lighter than the surrounding enstatite and are up to about 200µ in length (Fig. 1). Under electron bombardment in the electron microprobe, sinoite is easily recognized by its bright greenish luminescence. In each meteorite, ten different grains of the mineral were analysed qualitatively (Fig. 2) and quantitatively for silicon, nitrogen and oxygen by means of electron microprobe techniques using methods previously described². The quantitative analyses were carried out using sinoite from Jajh deh Kot Lalu as a reference standard. The results of these analyses are summarized in Table 1. The chemical identity of the compound in the four meteorites is apparent.