N Nacogdoches County: 70 Nash salt dome: 91 native elements: 8 native mercury: 8 native silver: 26, 89 nodule: 19, 44, 49 Nolan County: 20, 49, 63, 64, 65 north-central Texas: 43, 51, 52, 69, 70, 86, 88 O Oakville strata: 97 obsidian: 40, 77 occurrence of minerals: 14 ocher, red: 67 octahedral cleavage: 56, 57 oil shale: 88 olivine: 88 onyx: 84 öolitic limestone: 69 opal: 21, 29, 30, 31, 35, 37, 38, 78, 86 opaline granite: 72 opalized wood: 20, 78, 84 open-hearth furnace: 70, 72 Orchard salt dome: 91 Ordovician: 3, 55, 69, 84 orthoclase: 55, 61 P Packsaddle Mountain: 87 Packsaddle Schist: 87 Palangana salt dome: 91, 97 paleontologists: 2 parting of minerals: 17 Pavitte prospect: 53 Pecos County: 9 Pecos River: 65, 74, 75 pegmatite: 41, 55, 56, 58, 76, 77, 79, 81, 94, 95 Baringer Hill: 80 Pennsylvanian: 3, 45, 51, 55, 69, 70, 86, 88 peridotite: 88 period: 2 Permian: 1, 3, 20, 21, 43, 45, 49, 52, 55, 64, 65, 69, 86, 90 Permian basin: 42, 43, 65, 66 petrified wood: 20, 52, 78, 84 petrologists: 2 phenocrysts: 85 physiographic outline map: 42 pitchblende: 28, 95, 97 placer deposits: 60 Plata Verde mine: 90 Polk County: 98 porphyritic rocks: 45, 85 portland cement: 51, 69, 88 Precambrian: 2, 3, 44, 45, 48, 52, 53, 56, 58, 59, 60, 61, 63, 67, 72, 74, 75, 76, 79, 82, 85, 87, 93, 94, 95, 97 precious opal: 78 Presidio County: 45, 49, 57, 60, 62, 67, 77, 78, 84, 85, 90, 97 Presidio mine: 60, 90 properties of minerals: 14 pseudomorphs: 70, 87 pulverulent limestone: 41, 69 pumicite: 97, 98 pyramidal cleavage: 74 pyrite: 19, 26, 60, 70, 80, 87 pyrolusite: 27, 73, 74 pyroxene: 45 Q quartz: 8, 20, 29, 30, 31, 33, 36, 37, 38, 48, 51, 54, 56, 59, 60, 61, 68, 72, 78, 79, 80,81, 84, 85, 86, 94 agate: 21, 83, 84 amethyst: 37, 82 chalcedony: 16, 21, 45, 78, 81, 83, 86 chert: 19, 40, 81, 84 cryptocrystalline: 81, 84 jasper: 81, 84 milky: 82 onyx: 84 rock crystal: 82 rose: 82, 83 smoky: 82, 83 quartzite: 41, 74, 84, 86 Quaternary: 2, 3, 51, 79, 98 quicksilver (_see also_ mercury): 50 Quitman Mountains: 57, 58, 60, 62, 67, 82, 90 R radioactivity: 95, 96 Real County: 49, 51 Recent: 2, 3 “red beds”: 52 red ocher: 67 reef limestone: 1, 12 Reeves County: 65, 85, 91 reference books: 24, 39, 100 refraction, double: 46 rhombohedral cleavage: 46, 54 rhyolite: 40, 85 porphyry: 41, 85 Rio Grande: 83, 84, 97 rock— crystal: 82 gypsum: 40, 65 identification charts: 39 salt: 40, 65 units: 2 rocks, definition of: 8 Rodda, Peter U.: vii rose quartz: 82, 83 rosettes: 63, 64 Rustler Springs area: 91 rutile: 82