Pyroxene relations in two Hawaiian hypersthene-bearing basalts

Sum~tary. A preliminary account is given of an optical and electron-microprobe investigation i to the pyroxene relations of Hawaiian hypersthene-bearing lavas. It is shown that the clinopyroxene jackets to the phenocryst hypersthenes consist of strongly zoned augite, not pigeonite as former]y believed; the compositional range of this pyroxene isapproximately the same as that of the groundmass augite phase. Groundmass pyroxene relations are complex; in one case two distinct pyroxene phases, augite and pigeonite occur, in the other all compositions lying between augite and pigeonite are encountered