Ochre 57 9. Heavy, black, leaves a black or brownish black mark or streak when rubbed on a hard white rock or on unglazed porcelain. Manganese Ore 58 10. Heavy, with bright metallic luster, and lead-colored on a freshly broken surface. Galena 59 11. Looks like rosin, or may be ruby-colored or black, but has a high resinous luster on freshly broken surface. Sphalerite 60 12. Glassy luster; water-white, milky, honey-colored, pink, gray; may occur in six-sided crystals, sometimes pyramid-shaped; always breaks with flat glistening faces; always reacts in the lump with cold dilute muriatic (hydrochloric) acid. Calcite 16 13. Like calcite above but may have a pink, pearly luster and curved crystal faces; reacts with cold dilute acid when powdered but not readily in lump form. Dolomite 18 14. Opaque white, glassy or bluish, very heavy, lustrous on freshly broken surface; does not react with acid. Barite 61 15. Flaky, micaceous like “isinglass”. Mica 44 C. Specimens TOO HARD to be scratched readily on a fresh surface with a pocket knife or iron nail; weathered specimens may be slightly scratched. 1. Very fine-grained throughout, compact; occurs in nodules, pebbles; breaks with a slick, curved, oyster-shell-like (conchoidal) fracture. Chert, if white, gray or stained yellow or red 34 Flint, if black 34 Agate, if banded 37 Petrified Wood, if it shows the grain or bark of wood 37 2. Granular like sandstone but extremely hard and breaks through the grains as readily as around them. Quartzite 41 Quartzitic Sandstone 30 3. Fine-grained, dark green to dark gray to greenish black; occurs in boulders north of Missouri River and in the granite and porphyry country or southeastern Missouri. Basalt 46 4. Very fine-grained, compact, pink, red, brown, gray; usually “freckled” or sprinkled with grains about 1/16 inch in diameter. Porphyry 45 Rhyolite 45