![61.4 Hornblende-biotite schist. Michigan. Rock is composed of black needle-like grains of hornblende, brownish-black sheets of biotite, white feldspars, and gray quartz (only a few grains of quartz are visible). Sample courtesy of Sonoma State University Geology Department. [Scale shows cm divisions.]](../61.4.JPG)
61.4 Hornblende-biotite schist. Michigan. Rock is composed of black needle-like grains of hornblende, brownish-black sheets of biotite, white feldspars, and gray quartz (only a few grains of quartz are visible). Sample courtesy of Sonoma State University Geology Department. [Scale shows cm divisions.]