FIG. 4. Backscattered electron photomicrographs of iron oxides. A. Fragments of phyllite, quartz (qtz), and goethite (gt) embedded in a fine-grained matrix composed predominantly of goethite (sample M2-215). B. Angular fragments of goethite and quartz in a matrix composed of goethite and small grains of quartz and phyllite (sample M2-218).