Photomicrograph of fragment of basaltic rock, Kuskokwim region, Alaska, ca. 1943.

Photomicrograph of fragment of basaltic rock in rhyolite tuff, from locality in hills south of Juninggulra Mountain. The fragment has been silicified but the ophitic texture is preserved; above it is the corner of a large fragment of rhyolite lava; smaller fragments are biotite, muscovite formed from partly bleached biotite, and quartz. Flowage layers are formed close to the fragments. Plain light. Kuskokwim region, Alaska, ca. 1943. Published in U.S. Geological Survey Professional paper 268, Plate 16. 1955.