Gangue minerals included calcite, quartz, epidote, chlorite, and various zeolites. Strong regional scale alteration consists of pyrophyllite, chloritoid, muscovite, chlorite, quartz, rutile, and pyrite. Alteration has formed chlorite, epidote and sericite. It occurs in the quartz, albite, sericite, chlorite, garnet assemblage of pelitic schist. It often occurs intermixed with chlorite, muscovite, illite, cookeite, and kaolinite. Hornblende alters easily to chlorite and epidote. Important examples include the mica, chlorite, and the kaolinite-serpentine groups. The rocks commonly are altered to talc with carbonate or serpentine, chlorite, and magnetite. Hydrous minerals such as amphibole, zeolites, chlorite etc. It occurs interlayered with chlorite, biotite and phlogopite. Alteration products include mica, chlorite, and talc. The rock fragments include subrounded basalt, invariably replaced to various degrees by chlorite and epidote. Some sands contain magnetite, chlorite, glauconite, or gypsum. EPA has issued standards for bromate, chlorite, haloacetic acids and trihalomethanes. Garnets can be chemically altered and most often alter to serpentine, talc, and chlorite.