Photomicrograph of a porphyritic-aphanitic felsic rock. Plagioclase phenocrysts (white) and hornblende phenocryst (dark; intergrown with plagioclase) are set in a fine matrix of plagioclase laths that show flow structure. Plain polarized light; length of photo is 2.6 mm. "Most felsic rocks are porphyritic with phenocrysts that include plagioclase (most common), biotite, hornblende, orthopyroxene (rare), and orthoclase (rare) (fig. 4)." Middle Eocene Igneous Rocks in the Valley and Ridge of Virginia and West Virginia