6.1 Hornblende-biotite granodiorite. Sierra Nevada Batholith, US Highway 50 east of Kyburz, California. The rock consists of gray glassy quartz; small, white plagioclase feldspar grains; large, white, poikilitic alkali feldspar crystals; equant black biotite grains; and rectangular to diamond-shaped, black hornblende crystals. Just below the scale, an amoeboid poikilitic grain of alkali feldspar reflects light from its surface.