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Contents

Abstract. 5

Introduction. 5

Relationship between Agate, Chert, and Quartzite. 7

Regional Geode Sites. 9

Regional Stratigraphy of the Mississippian. 9

Mississippian—Iowa-Missouri-Indiana Region. 9

Mississippian—Kentucky. 16

Mississippian—The Ouachita Mountains Novaculite. 21

Formation of the Cherts—Case Studies. 27

Overview of Oceanic Nodule Formation. 27

The Lake Magadii chert. 28

Windalia Radiolarite, Australia. 29

Succor Creek, Oregon Ash and Cherts. 34

The Cherts of Milos Greece. 35

The Phosphoria Formation of Idaho-Montana-Wyoming. 36

Formation of the Kentucky Glauconite Agates. 38

Iowa Geode/Nodule Structures and Inclusions. 45

Agate. 48

Anhydrite. 49

Calcite. 50

Chert. 50

Fluorite Pseudomorphs. 51

Oolites. 52

Kentucky Nodule/Geode Compositional Types. 53

Glauconite Nodule/Geode. 53

Limestone and Glauconite Nodule/Geode. 53

Barite Nodule/Geode. 54

Apatite Nodule/Geode. 55

Hematite Nodule/Geode. 56

Anhydrite Nodule/Geode. 57

Kentucky Nodule/Geode Structural Types. 61

Hash Nodule/Geode. 61

Concentric Nodule/Geode. 62

Tubular Nodule/Geode. 63

Kentucky Geode/Nodule Structures and Inclusions. 65

Allophane. 65

Anhydrite. 67

Apatite. 68

Benthic Fossils. 69

Calcite. 69

Black Agate Centers (Chalcopyrite, Millerite, Humic Acid). 70

Chalcopyrite. 71

Conodonts. 72

Coronas. 73

Dendrites (Magnetite). 74

Dolomite. 75

Glauconite. 76

Glauconite Shell 80

Foraminifera. 81

Hematite Microspheres. 81

Hematite Plates. 82

Holospheres. 82

Humic Acid. 84

Illite (Clay) Microspheres. 84

Imogolite. 85

Iron Microspheres. 87

Iron Reduction Center Banding. 88

Kaolinite (Clay). 89

Millerite. 90

Pyrite. 91

Saddle Dolomite. 92

Smoky Quartz. 94

Syneresis Texture. 95

Overview of the Kentucky and Iowa Geode Geology. 97

General Iowa Geode Conclusions. 97

Candidate Kentucky Geode Conclusions. 97

Candidate Keokuk, Iowa Sources. 97

Further Reading. 97

Kasper Jasper Press Titles. 98

 

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