Chemical composition of altered chromites from the Stillwater Complex, Montana

TLDR: In this paper, the parent chromite and ferritchromit can be expressed by the general formula (Mg, l-e,+) (Cr, Al, Fe3+)rOr, and neither contains cation deficiencies of the maghemite type.

Abstract: Small amounts of very iron-rich chromite are formed as an alteration product of normal cumulus chromite accompanying the alteration of primary silicates to chlorite in the Stillrvater Complex, Montana. We have analyzed two parent chromite-ferritchromit pairs from the Stillwater Complex b1'a combination of wet and microprobe methods; both the parent chromite and ferritchromit can be expressed by the general formula (Mg, l-e,+) (Cr, Al, Fe3+)rOr, and neither contains cation deficiencies of the maghemite type. The alteration is essentially a volume-for-volume replacement of MgO and AbOr by FeO and !'erOr; content is oniy slightly different in the primary and secondary phases.