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| Obsidian beads |
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| Pliny's Natural History features volcanic glass called "Obsidianus", so named from its resemblance to a stone found in Ethiopia by one Obsius. Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline; in addition, its composition is too complex to comprise a single mineral. It is sometimes classified as a mineraloid. Though obsidian is dark in color similar to mafic rocks such as basalt, obsidian's composition is extremely felsic. Obsidian consists mainly of SiO2 (silicon dioxide), usually 70% or more. Crystalline rocks with obsidian's composition include granite and rhyolite. Because obsidian is metastable at the Earth's surface (over time the glass becomes fine-grained mineral crystals), no obsidian has been found that is older than Cretaceous age. This breakdown of obsidian is accelerated by the presence of water. Obsidian has low water content when fresh, typically less than 1% water by weight, but becomes progressively hydrated when exposed to groundwater, forming perlite. Tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, though few scientists now adhere to this hypothesis. Pure obsidian is usually dark in appearance, though the color varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black color. A very few samples are nearly colorless. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). It may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden sheen (sheen obsidian) or a rainbow sheen (rainbow obsidian). |
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| Displaying 1 to 15 (of 15 products) |
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OBS16 15-16 inches flat oval Obsidian beads strand
$2.74 - $4.10
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OBS15 15-16 inches puff round Obsidian beads strand
$1.46 - $2.18
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OBS14 15.5-16 inches faceted octagon Obsidian beads strand
$3.66 - $5.46
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OBS12 15.5 inches rice Obsidian beads strand
$2.93 - $4.37
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OBS11 15.5 inches 4*8mm rondelle Obsidian beads strand
$2.93 - $4.37
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OBS10 15.5 inches 9*13mm gourd Obsidian beads strand
$2.93 - $4.37
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OBS09 15-16 inches heart Obsidian beads strand
$1.83 - $2.73
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OBS08 15-16 inches faceted ball Obsidian beads strand
$2.74 - $4.10
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OBS07 wholesale black obsidian beads strand, 8mm, round
$1.39 - $2.07
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OBS06 wholesale black obsidian beads strand, 18mm, round
$3.88 - $5.80
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OBS05 wholesale black obsidian beads strand, 16mm, round
$3.33 - $4.97
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OBS04 wholesale black obsidian beads strand, 14mm, round
$2.77 - $4.14
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OBS03 wholesale black obsidian beads strand, 12mm, round
$2.40 - $3.59
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OBS02 wholesale black obsidian beads strand, 10mm, round
$1.66 - $2.48
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OBS01 wholesale black obsidian beads strand, 6mm, round
$0.92 - $1.38
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| Displaying 1 to 15 (of 15 products). |
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