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Agate

Filed under: regular postings — Gary June 1, 2010 @ 8:34 am

AgateLady.com

Agate

Agate

I bumped into Karen recently and she told me about her love for agates.  As well she told me about a book she was releasing…

Agate Book

The Gitche Gumee Museum Announces the Publishing of a New Agate Book
A new book “Agates: Inside Out” will be available in June.  The book helps readers to think like an agate so they can be more successful in finding them.
Grand Marais, MI April 1, 2010 – After the first agate book Understanding and Finding Agates was published in 2004 rockhounds said they wanted more information.  Staff at the Gitche Gumee Agate and History Museum launched an intensive research effort.  Data was compiled and written in a non-technical manner to explain what agates are, how they formed, and how to look for them.

The book features photographs taken by Thomas P. Shearer.  He uses innovative techniques that have never before been employed to take pictures of minerals.  Also included are helpful diagrams that illustrate how agates formed.

Unlike the first book that primarily focused on Lake Superior agates, this new book covers agates from all over the world.  There is also detailed information and photographs of over 30 different types of agate structures and banding patterns.

Karen Brzys, owner of the Gitche Gumee Museum, and Tom Shearer, owner of ColdStone Photography LLC, hope to team up with other educational and entertainment products aimed at the dedicated and growing number of rockhounds.  Some of these future products may include DVDs, post cards, and calendars.

Advance orders for the book are now being accepted.  The book is currently at the printer and will be available for shipment by the end of May or early June.  To place an advance order or to see additional information about the new agate book, please visit www.agatelady.com.  All book sales benefit the museum.

The Gitche Gumee Museum was operated by Axel Niemi from 1954 until 1978.  Karen Brzys, who spent time in the museum as a child, purchased and renovated the building and reopened the museum in 1999.  The museum is open mid-May through September, or by appointment.  Please visit www.agatelady.com for more information about the museum.

Contact:
Karen Brzys, Owner and Curator
Gitche Gumee Museum
21739 Brazel Street
PO Box 308
Grand Marais, MI 49839
906-494-2590 office
906-494-3000 museum

http://www.agatelady.com

Karen@agatelady.com

More about whats in the book, click below:

CHAPTER 1: What Is An Agate?  . . . . . . . . . . . . . . . . . . . . . . . . . . . .     1
A BASIC DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     1
AGATES AND HUMAN HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
AGATES AND THEIR “FIRST COUSINS” . . . . . . . . . . . . . . . . . . . . . .     4
Macrocrystalline Quartz  . . . . . . . . . . . . . . . . . . . . . . . .     4
Fibrous Microcrystalline Quartz. . . . . . . . . . . . . . . . . . .    8
Granular Microcrystalline Quartz . . . . .  . . . . . . . . . . . .    9
Silicified Fossils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    10
QUARTZ PROPERTIES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    14

CHAPTER 2: How Did Agates Form?. . . . . . . . . . . . . . . . . . . . . . . . .    16
THE EARTH — IN THE BEGINNING. . . . . . . . . . . . . . . . . . . . . . . . . . .    16
AGATE FORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    21
INFLOW AGATE GENESIS THEORY. . . . . . . . . . . . . . . . . . . . . . . . . .    24
Possible Sources of Silica . . . . . . . . . . . . . . . . . . . . . . .    28
Silica Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    31
Infiltration Channels. . . . . . . . . . . . . . . . . . . . . . . . . . . .    34
Concentric Banding . . . . . . . . . . . . . . . . . . . . . . . . . . . .    41
Horizontal Banding  . . . . . . . . . . . . . . . . . . . . . . . . . . . .    55
SILICA GEL AGATE GENESIS THEORY . . . . . . . . . . . . . . . . . . . . . . .    57
AGATE GENESIS CONCLUSIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . .    60
Silica Gel Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    60
Inflow Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     62
TYPES OF HOST ROCK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    65
Igneous Rock Agates . . . . . . . . . . . . . . . . . . . . . . . . . . .    67
Amygdaloidal Agates . . . . . . . . . . . . . . . . . . . . . . . . . . .    67
Rhyolitic Agates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    70
Sedimentary Rock Agates . . . . . . . . . . . . . . . . . . . . . . .    73
TIMING OF AGATE FORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . .    76

CHAPTER 3: How Do You Find Agates? . . . . . . . . . . . . . . . . . . . . . .    82
A POCKET FILLED IN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    88
BANDING AND OTHER PATTERNS . . . . . . . . . . . . . . . . . . . . . . . . . .    90
TRANSLUCENCY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    93
COLOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     95
SHAPE, SIZE, AND WEIGHT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     106
LUSTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    109
HUSK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    112
CONNECTIVE CHANNELS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    118
PSEUDOBANDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    120
AGATE-WANT-TO-BE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    122
Chert , Flint, and Jasper . . . . . . . . . . . . . . . . . . . . . . . .    122
Metamorphic Rocks  . . . . . . . . . . . . . . . . . . . . . . . . . . .    126
Secondary Fills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    127
Silicified Fossils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     128
Other Agates -Want-To-Be . . . . . . . . . . . . . . . . . . . . . .    132
CARING FOR AND CLEANING AGATES . . . . . . . . . . . . . . . . . . . . . .     135
ASSESSING THE VALUE OF AGATES. . . . . . . . . . . . . . . . . . . . . . . .    138

CHAPTER 4: What Are the Different Types of Agate? . . . . . . . . . . .    139
BOTRYOIDAL (GRAPE) AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . .    139
BRECCIATED (MOSAIC) AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . .    140
CANDY STRIPED AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    141
CARNELIAN AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    142
CLOUD AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    144
CRAZY LACE AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    144
DENDRITIC AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    146
ENHYDRO (WATER-FILLED) AGATES . . . . . . . . . . . . . . . . . . . . . . . .    150
EYE AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    151
FIRE AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    156
FLAME AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    158
FLOATER BAND AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    159
FORTIFICATION AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    159
GEODE AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    161
IRIS (RAINBOW) AGATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    162
JASPER AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    165
MOSS AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    165
PAINTSTONE AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    168
PEELER AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    168
PLUME AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    170
POLYHEDROID AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    172
PSEUDOMORPH AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    173
RUIN AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    174
SAGENITE AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    175
SARDONYX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    177
SEAM AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    178
SHADOW AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    180
STALK AGGREGATE AGATES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    182
Thunder Egg Agates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    182
Tube Agates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    184
Water -Level Agates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    186

CHAPTER 5: Where Can You Find Agates?. . . . . . . . . . . . . . . . . . . .    187
A SELECTION OF UNITED STATES AGATES. . . . . . . . . . . . . . . . . . .    187
A SELECTION OF INTERNATIONAL AGATES . . . . . . . . . . . . . . . . . .    212

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    231
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    239
MUSEUM INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    243
HOW TO VOTE FOR YOUR FAVORITE PHOTOgraph. . . . . . . . . .    244
INFORMATION ABOUT AGATE DVDS & OTHER PRODUCTS . . . .    244
Rock hunting log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    245

CHAPTER 1  What Is An Agate?

A BASIC DESCRIPTION

One of the most intriguing forms of quartz produced by nature is the semi-precious gemstone, agate.  It is a variegated form of chalcedony (pronounced kal-sed’-nee), which is a type of microcrystalline quartz made of silicon dioxide (SiO2).2 Microcrystalline means that the crystals are so small that they cannot be seen with the naked eye or with a normal optical microscope.3 In fact, the only way to see actual agate crystals is to use powerful technology such as transmission electron microscopy TEM or scanning electron microscopy SEM.4

Agates naturally develop when empty pockets or veins inside host rock fill in molecule-by-molecule and layer-by-layer as quartz microcrystals self-organize to form concentric bands or other patterns.  Agates can be found in igneous, sedimentary, and metamorphic rocks and have been discovered on every continent.5 They can be collected from deserts, mountains, rivers, shorelines, gravel pits, prairies, and fields.

Agates are technically classified as sedimentary because they are deposited in empty pockets with silica from mineral-rich fluids or gels.6 The colors and arrangement of microcrystals are influenced by changes in pressure, temperature, and mineral content that occur during the formation process.7 Unlike other gemstones, each agate is unique.  Even slabs cut from the same specimen will vary.

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