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Contents

INTRODUCTION.. 6

JASPER, AGATE, OPAL AND OTHER DEFINITIONS. 6

LITERATURE SILICA CLASSIFICATION.. 8

BANDED AGATE SERIES. 9

BANDED AGATE TYPES DISCUSSION.. 10

AGATE/CHALCEDONY IDENTIFICATION BY BANDING.. 10

RELATIONSHIP BETWEEN THE AGATES, JASPERS, CHERTS, AND QUARTZITES. 11

JASPER-AGATE RELATIONSHIPS. 15

OPAL-AGATE RELATIONSHIPS. 17

CLASSIFICATION KEY. 18

A CLASSIFICATION OF SILICA BANDING SYSTEMS. 21

AN AGATE IONIC DEPOSITION MODEL. 51

AGATE MAJOR AND MINOR BANDING.. 54

PARTICULATE SYSTEMS (MONODISPERSIONS) 56

AGATE CLAY MICROSTRUCTURE MODELS. 60

AGATE MICROSTRUCTURES. 62

BANDING HEMISPHERES, HEMISPHERE-CONES, AND TEE-PEE STRUCTURES. 69

Banding Hemispheres. 69

Hemisphere-cones. 70

Tee-Pees. 70

Hemispheres pointing to the agate interior (center) 72

Hemispheres pointing to the agate exterior. 72

AGATE/CHALCEDONY SITE POLARIZING MICROSCOPY ANALYSIS. 74

TUBE OF ENTRY CONTRADITIONS. 78

KEY ITEMS TUBES OF ENTRY DO NOT EXPLAIN.. 83

DILATION MINERALIZATION INTRUSIONS. 84

BANDING DEFORMATION THAT ARE NOT DILATIONS. 86

Banding Cones. 86

Banding Pinchout 87

SHELL EXSOLUTION STRUCTURES. 87

GEODE STRUCTURES INDICATING SILICA EXSOLUTION FROM A MELT. 90

STRUCTURES INDICATING QUIESENCE IN AGATES. 94

Silica quiescence—filaments. 94

Silica quiescence—plumes. 95

Silica quiescence—pendants. 95

HIGH TEMPERATURE MINERALIZATION IN AGATES. 96

Elliptical-botryoidal vugs in vein agate. 96

Holospheres--allophane. 96

Central mineralization—ilmenite ((Fe,Mg,Mn,Ti)O3) / rutile (TiO2) 97

Central mineralization—millerite (NiS, Nickel Sulfide) 99

Central mineralization—quartz scepters. 99

Central mineralization—tridymite/cristobalite. 100

NON-DILATION STRUCTURES FROM MINERAL AND SILICA VOID ENTRY. 102

Calcite Intrusion—Hemispheres. 102

Zeolite Intrusion—Hemispheres. 103

Silica-calcite Intrusion—Caliche. 104

Groundwater Intrusion—Hematite. 106

Silica Intrusion—Carnelian. 107

Silica Intrusion—Chevron Banding. 108

Silica Intrusion—Dissolution. 111

Silica Intrusion—Banding Deformation-Dissolution. 112

Silica Intrusion—Implosions with perlite/celadonite. 113

Silica Intrusion—Implosions with quartz. 114

Silica Intrusion—Opal 114

Silica Intrusion—Sericite Intrusions. 115

Silica Intrusion—Stalactites. 116

Silica Intrusion—Tubes. 117

Silica Intrusion—Vent Cones. 119

Water Migration—PSL Tubes. 120

Water Migration—Arterial Tubes. 121

AGATE BANDING STRUCTURES. 121

PRIMARY SILICA LAYER (PSL) STRUCTURE. 127

SELECTED AGATE SPECIMENS UNDER THE POLARIZING MICROSCOPE. 131

CHEVRON STRUCTURES. 136

BANDING KINK STRUCTURES. 140

Banding Kink Fractures. 140

Banding Kink Dilations. 141

Banding Kink Mineral Zoning. 142

BANDING DISSOLUTION STRUCTURES. 143

BANDING ON PARTICULATE SURFACES. 146

WATERLINE TILTS. 148

WATERLINE STRUCTURES. 149

WATERLINE BANDING-PRIMARY SILICA LAYER JOIN.. 154

BANDING COMPRESSION (PINCHOUTS) 156

AGATE STRUCTURES THAT INDICATE A PLASTIC (GEL) OCCURRENCE. 158

Silica Intrusions—chevron spirals. 158

Silica Intrusions—feather agate (feathers) 159

Gel behavior—silica shift 160

Gel behavior—silica flow structures. 160

Gel behavior—mineral migration. 161

Gel behavior—hemisphere settling. 161

Gel behavior—banding penetration. 162

Gel behavior—syneresis crumpling. 162

Gel behavior—mineral wall detachment 164

Gel behavior—orb shell detachment 164

Gel behavior—waterline detachment 165

Gel behavior—ramped waterlines (gel shearing) 167

Gel behavior—gooseneck extrusions. 167

Gel behavior—pressure ridge extrusions. 169

Gel behavior—chevron formation. 169

Gel behavior—quartz core settling. 172

Gel behavior—shell expansion. 172

Gel Behavior—soft sediment deformation (ruin structure, shearing) 174

Gel behavior—banding tilt and sag. 175

Gel behavior—banding folding and dissolution. 176

Gel behavior—banding extinction. 177

Gel behavior—sedimentation. 177

Gel behavior—banding compaction/banding expansion. 179

Gel behavior—banding clay desiccation. 180

AGATES WITH CENTRAL STRESS FRACTURING.. 180

AGATES AND JASPERS WITH STRUCTURES LISTED AS BIOLOGICAL IN THE LITERATURE. 182

Tubes in Geodes/Thundereggs/Amygdules. 182

Tubes in jasper and agate. 187

AGATE BANDING INCLUSIONS AND STRUCTURES. 188

AGATE PRIMARY SILICA LAYER FRACTURE (RENT) STRUCTURES. 208

Rents with no flow on the long axis. 209

Spheroids confused as tubes of entry. 210

Rents that are not veinlets, just fractures in the primary silica layer. 211

Rents (veinlets) that breach the primary silica layer, but do not form dilations. 211

Rents that end up in waterlines not dilations. 212

Rents that created hemispheres, not dilations. 213

Rents with late mineral intrusion. 215

Shell fractures (veinlets) that have late stage inflow of celadonite and chlorite. 216

AGATE GEODE VOLCANIC SHELL FRACTURES. 217

Shell fractures (veinlets) that do not breach the primary silica layer. 217

Shell fractures (veinlets) that deposited underneath the primary silica layer. 218

Shell fractures (veinlets) that are not silica. 218

Shell fractures (veinlets) that are themselves banded. 219

Shell fractures (veinlets) with different mineralization than connecting rents. 220

BANDED AGATE DILATION STRUCTURES. 221

Dilation structures with micrograins and hemispheres. 221

Dilation as central banding. 222

Dilation indicating outflow.. 223

Dilations indicating symmetrical outflow.. 224

Dilations--the lack of microspheres. 225

Banding kinks mimicking dilations. 226

Dilation structures with multiple rents. 226

Dilations against waterlines. 227

Dilations with chevron banding. 228

Dilations not adjacent to the primary silica layer (PSL) 229

Dilations with waterlines/dilations with banding underneath/gel quiescence. 229

Dilations with crumpled banding/dilations with banding underneath/gel quiescence. 230

Styolitic banding deformation without a dilation. 231

Dilation interiors blocked by wall-banding. 232

Dilation bifurcation around inclusions. 232

Opposing dilations without turbulence. 234

Dilation-tube structures. 234

Dilations around hash sediment accumulations. 235

Dilations above waterlines. 236

Waterline agates with no dilations. 237

Two-stage dilations. 238

Laminar banding in dilations. 240

Dilation as a fold structure. 242

CHERT AND CHERT-AGATE (CHALCEDONIC CHERT) STRUCTURES. 244

Pinchouts in banding without related dilation structures. 245

Pinchouts in only a single silica band. 246

The Primary Silica Layer in Sedimentary Agates. 247

SURFACE TENSION EFFECTS IN THE CHERTS AND AGATES. 249

BANDED AGATE WITH FEW TUBE STRUCTURES. 252

Specimens with few banding tubes from Dryhead, Montana. 253

Specimens with few banding tubes from Fairburn, South Dakota. 256

EQUIPMENT USED.. 257

DOING THE MATH—HOW LONG DOES IT TAKE TO MAKE AN AGATE?. 258

AUTHOR’S BACKGROUND.. 258

INDEX. 261

THANKS. 263

KASPER JASPER PRESS TITLES. 264

 

 

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