Geology of the Little Black Peak quadrangle, Lincoln and Socorro Counties, New Mexico [reprint]

green phenocrysts of olivine. In thin section a very crude trachytic texture is discernible particularly around the olivine phenocrysts. The principal minerals are calcic labradorite (An„-An7„), titaniferous diopsid-ic augite, olivine (Fa-Fa 23), and magnetite. Altera- tion is very slight, hematite being the only identifiable secondary product. Reddish-brown rims on a few of the olivine crystals may be iddingsite, but the develop- ment is too fine grained for certainty in the determina-tion. A complete chemical analysis of a sample of the Little Black Peak flow was published by Allen (1951) and showed: