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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QUARTZ CRYSTAL CLUSTER SOURCE UNKNOWN

AU $8.99 (0 Bids)
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976 Gram HIMALAYAN ROSE QUARTZ ROUGH STONE

AU $18.00
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Quartz Calcium Stalactite 5.1cm x 1.8cm Australian Seller FREE postage

AU $23.50
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Spirit Quartz Amethyst Crystal Cluster from South Africa. 6 x 4 cm.

AU $18.00
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Quartz Crystal Mineral Specimen From Mount Isa Queensland Natural Crystal 67 gr

AU $8.95
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15g Rare natural red quartz crystal reiki healing cluster original ore AU101

AU $0.01 (1 Bid)
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25g Rare natural red quartz crystal reiki healing cluster original ore AU100

AU $0.28 (3 Bids)
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Some of the common varieties of chalcedony are:

   

Chalcedony specimens now available (at eBay):

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157.5ct/31.5g Stilbite Chalcedony Apophyllite Mineral Display Specimen ASC237

AU $9.99 (0 Bids)
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423.5ct/84.5g Chalcedony Stilbite Mordenite Geode Mineral Display Specimen CS336

AU $12.99 (0 Bids)
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82.5g Yellow Apophyllite on Chalcedony Mineral Specimen Zeolite India AC413

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115ct/23g Sugary White Chalcedony Mineral Display Specimen Zeolite - C515

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54ct/11g Small White Chalcedony Stalactites Mineral Display Specimen Zeolite

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212ct/42.5g Chalcedony Plate Geode Mineral Display Specimen India Zeolite C519

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11g Blue Chalcedony w/ Mordenite Stalactite Mineral Specimen Zeolite India C517

AU $9.99 (0 Bids)
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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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AUSTRALIAN GEMSTONES IN COLOUR HandB 41 gemstones + origin opal color PERRY 1973

AU $15.25
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Handmade Necklace Round Boulder Opal Bead and Tiger's Eye Necklace on Hemp Cord

AU $20.00
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Wood and Doublet Opal Silver Plated Artistic Necklace. Lapidary, Hobby, Gift

AU $18.00
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Wood and Doublet Opal Silver Plated Artistic Necklace - Lapidary, Hobby, Gift

AU $9.00
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Boulder Opal Necklace With 925 Stirling Silver Cross Inlay Lapidary Hobby, Gift

AU $15.00
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Beautiful Oval Opal Doublet, Free Form Shape 925 Stirling Silver Pendant - Gift

AU $37.00
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Lapidary: 2.1 carat Oval Cabochon Ethiopian Welo Opal. Solid Natural Opal Africa

AU $28.00
End Date: Tuesday May-15-2018 11:11:25 EST
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