C—yellow-brown H—5.5 (may be as In earthy masses; Limonite (29) to black low as 1) coloring material in FeO(OH)·H₂O S—yellow-brown Cl—none many sandstones, F—uneven conglomerates, and soils; often mixed with and difficult to distinguish from goethite and other iron minerals C—brassy yellow H—6 As compact masses, Pyrite (28) S—greenish black Cl—poor grains, cubes, and in 8- FeS₂ F—conchoidal to and 12-sided crystals; uneven commonly associated with coal, and with lead-zinc ores of northwestern Illinois C—pale brassy H—6 As fibrous, radiating, Marcasite yellow to Cl—poor tabular, and cocks-comb FeS₂ (28) silver white F—uneven crystals or compact S—greenish gray masses; usually lighter colored than pyrite, but difficult to distinguish from pyrite; associated with coal, and with lead-zinc ores of northwestern Illinois II. NONMETALLIC LUSTER, STREAK WHITE A. Hardness not greater than 2 (can be scratched by fingernail) C—usually white H—2 Commonly found in Gypsum (26) but may be Cl—perfect in Illinois as twinned or CaSO₄·2H₂O almost any color one direction, needle-shaped crystals less perfect in in weathered shales two others containing pyrite and calcium carbonate C—white or a H—2 As needle-shaped Melanterite shade of green crystals or powdery FeSO₄·7H₂O coating on pyrite or marcasite; has an astringent taste B. Hardness greater than 2 but not greater than 3 (Can be scratched by a penny)