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Preface vii
Introduction 1
Earth’s outer crust 2
Geologists 2
Time and rock units 2
Geologic map 6
What are rocks and minerals? 7
Chemical elements 7
Minerals 7
Rocks 8
Igneous rocks 9
Extrusive or volcanic igneous rocks 9
Intrusive igneous rocks 9
Sedimentary rocks 10
Soils 10
Sedimentary rock materials in broken fragments 11
Sedimentary rock materials in solution 12
Cementing materials and chemical sediments 12
Sedimentary rocks formed by plants and animals 12
Metamorphic rocks 12
Static metamorphism 13
Contact metamorphism 13
Dynamic metamorphism 14
Occurrence and properties of minerals 14
How minerals occur 14
Crystalline minerals 14
Crystals 14
Imperfect crystals 14
Amorphous minerals 15
Some distinguishing properties of minerals 15
Color 16
Luster 16
Transmission of light 16
Hardness 16
Streak or powder 17
Cleavage 17
Parting 17
Fracture 17
Specific gravity 18
Effervescence in acid 18
Some special occurrences of minerals 18
Cave deposits 18
Concretions 19
Geodes 19
Petrified wood 20
Collecting rocks and minerals 22
Rock and mineral identification charts 24
How to use the mineral identification charts 24
Key to mineral identification charts 25
Mineral identification charts 26
How to use the rock identification charts 39
Rock identification charts 40
Descriptions of some Texas rocks and minerals 43
Anhydrite 43
Asbestos 43
Barite 44
Basalt 45
Calcite 46
Cassiterite 47
Celestite 48
Cinnabar 49
Clay 51
Copper minerals (chalcocite, chalcopyrite, malachite, azurite)
52
Dolomite 54
Feldspar 55
Fluorite 56
Galena 57
Garnet 58
Gneiss 59
Gold 59
Granite 61
Graphite 62
Gypsum 63
Halite 65
Hematite 66
Limestone 68
Limonite 70
Llanite 71
Magnetite 72
Manganese minerals (braunite, hollandite, pyrolusite) 73
Marble 75
Mica 76
Obsidian and vitrophyre 77
Opal 78
Pegmatite 79
Pyrite 80
Quartz 81
Quartzite 84
Rhyolite 85
Sand and sandstone 85
Schist 87
Serpentine 87
Shale 88
Silver minerals (argentite, cerargyrite, native silver) 89
Sulfur 90
Talc and soapstone 93
Topaz 94
Tourmaline 94
Uranium minerals (carnotite, uranophane, pitchblende) 95
Volcanic ash (pumicite) 97
Composition, hardness, and specific gravity of some Texas minerals
99
Books about rocks and minerals 100
Nontechnical books for beginners 100
Textbooks and other reference books 100
Selected references on Texas rocks and minerals 100
Glossary 102
Index 104