C—white, gray, H—3.5 Relatively heavy; Witherite light yellow Cl—in one effervesces in acid; BaCO₃ direction associated with fluorite F—uneven and barite in southern Illinois but is not abundant C—white, pink, H—3.5 In grains, rhombohedral Dolomite gray, or light Cl—perfect in crystals and cleavable CaMg(CO₃)₂ brown three or granular masses; directions, not effervesces slowly in at right angles cold acid when powdered, (rhombohedral) more vigorously in warm acid; principal mineral in rock called dolomite C—colorless, H—3.5 In fibrous or compact Cerussite white, gray, masses or may be in PbCO₃ grayish black orthorhombic crystals as a coating on galena; very heavy; effervesces in acid; formed by alteration of galena C—brown to gray H—3.5 In fibrous or botryoidal Siderite S—usually white Cl—in three masses or rhombohedral FeCO₃ but may tend directions not crystals; effervesces in toward brown at right angles hot acid when weathered (rhombohedral) slightly curved surfaces C—yellow, H—3.5 In crystals, in fibrous Sphalerite yellow-brown to Cl—parallel to or layered masses; ZnS (30) almost black dodecahedral associated with galena S—light yellow faces; in six in northwestern to brown directions Illinois, with fluorite and galena in southern Illinois C—colorless, H—4 In cubes and cleavable Fluorite (25) white, yellow, Cl—perfect, masses; many colors; (Fluorspar) purple, green, parallel to mined in Hardin and Pope CaF₂ blue octahedral counties faces; in four directions C—white, tinted H—5 As crystalline Smithsonite yellow, blue, incrustations or in ZnCO₃ or green earthy or compact masses; associated with fluorite-sphalerite ores in southern Illinois, with galena and sphalerite in northwestern Illinois D. Hardness greater than 5 but not greater than 7