Timerock Fossils, Crystals & Minerals

The Varieties of Silica:
Quartz, Chalcedony & Opal

Quartz, chalcedony and opal are all forms of silica (SiO2). The difference is that quartz has visible crystals whereas chalcedony crystals can only be seen under a microscope and opal has no crystals at all.

Quartz is, by far, the most common mineral on earth. 

There are hundreds of varieties of quartz, chalcedony and opal, mostly distinguished by their color.

 

Some of the more common varieties of quartz are:

 

Quartz specimens now available (at eBay):

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Pyrite, Sphalerite and Quartz Crystals

AU $0.99 (0 Bids)
End Date: Thursday Aug-23-2018 19:50:01 EST
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QUARTZ CRYSTAL CLUSTER SOURCE UNKNOWN

AU $2.99 (0 Bids)
End Date: Tuesday Aug-21-2018 15:57:57 EST
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Mooralla quartz crystal

AU $25.00 (0 Bids)
End Date: Thursday Aug-23-2018 14:39:22 EST
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383gNatural Skeletal Purple Quartz AMETHYST Geode Specimen From Brazil

AU $1.04 (2 Bids)
End Date: Wednesday Aug-22-2018 19:43:51 EST
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Molybdenite on Quartz mineral specimen

AU $9.99 (0 Bids)
End Date: Tuesday Aug-21-2018 14:08:56 EST
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Grape AGATE Chalcedony with Quartz - Indonesia - 4.5x4.5x1.5cm 21g NICE

AU $12.90
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Some of the common varieties of chalcedony are:

   

Chalcedony specimens now available (at eBay):

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Grape AGATE Chalcedony - Indonesia - 5x2.8x2.5cm 20g NICE

AU $13.90
End Date: Saturday Sep-15-2018 18:26:30 EST
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Grape AGATE Chalcedony - Indonesia - 5x4.3x3.5cm 38g NICE

AU $17.90
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Grape AGATE Chalcedony - Indonesia - 5.5x3.5x1.9cm 19g NICE

AU $13.90
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Grape AGATE Chalcedony - Indonesia - 5.5x2.1x2.1cm 17grams NICE

AU $13.90
End Date: Saturday Sep-15-2018 18:13:34 EST
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36g Pink Stilbite on Blue/Grey Chalcedony Mineral Specimen Zeolite CS334

AU $9.99 (0 Bids)
End Date: Tuesday Aug-21-2018 20:29:36 EST
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Grape AGATE Chalcedony - Indonesia - 5x2x1.5cm 12grams NICE

AU $11.90
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Grape AGATE Chalcedony - Indonesia - 5x3.x2cm 24grams NICE

AU $15.00
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Some opal displays different colors when viewed from different directions. Any opal which exhibits this play of colors is called "precious opal"; opal which does not exhibit a play of colors is called "common opal". Some of the common varieties of opal are:

Opal specimens now available (at eBay):

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Boulder Opal Rough Natural Solid Koroit Yowah Australian 214 ct

AU $14.00 (0 Bids)
End Date: Tuesday Aug-28-2018 18:14:46 EST
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Boulder Opal Rough Natural Solid Koroit Yowah Australian 275 ct

AU $14.00 (0 Bids)
End Date: Tuesday Aug-28-2018 18:10:58 EST
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Boulder Opal Rough Natural Solid Koroit Yowah Australian 281 ct

AU $20.00 (0 Bids)
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Striped Boulder opal display mineral specimen lapidary rough skin polish TB364

AU $125.00
End Date: Monday Sep-17-2018 13:40:33 EST
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850g Boulder opal mineral specimen collection lapidary rough skin polish BO01

AU $95.00
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Boulder opal mineral specimen collection lapidary rough skin polish TB363

AU $95.00
End Date: Monday Sep-17-2018 11:44:34 EST
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Opal in natural rock matrix

AU $35.50 (0 Bids)
End Date: Friday Aug-24-2018 22:03:07 EST
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