Geology and Mineral Resources of Paraguay A Reconnaissance

IGNEOUS AND METAMOEPHIC ROCKS 49FIGURE 40. Shonkinite (specimen P-54f) from Mbocayaty. Near the upper edge are two large hydronephelite replacements, h, of nepheline. The replacementnear the middle appears to be isotropic analcite. Feldspar, /, is inconspicuous, forming the groundmass of the crowded pyroxene, p, olivine, o, biotite,and other crystals. X 15.FIGURE 41. Shonkinite (specimen P-54g) from Mbocayaty. Diopsidic pyroxene, p, augite; olivine, o; brown biotite, b; iron oxide; and euhedral hydronephelite,ft all in clear matrix of sanidine. X 15.