Figure F12. Photomicrographs of diatom clay and diatom-bearing clay. A. Dark gray diatom-bearing clay with iron sulfides (pyrite) giving a distinctive color to the sediment (Sample 188-1165B-14H-5, 40-42 cm). B. Greenish gray diatom clay showing well-preserved diatoms and sponge spicules with little quartz silt (Sample 188-1165B-14H-6, 60-62 cm).