Obsidian beads

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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OBS07 8mm round black obsidian beads strand wholesale
OBS07
The bead is black obsidian, A grades, round shape, 8mm, about 15 inches long, about 49 beads. The listed price is for one strand beads. Obsidian is vo...

Start From: 5 Unit(s)
US$2.16 - US$2.54

OBS06 18mm round black obsidian beads strand wholesale
OBS06
The bead is black obsidian, A grades, round shape, 18mm, about 15.5 inches long, about 22 beads. The listed price is for one strand beads. Obsidian is...

Start From: 5 Unit(s)
US$5.68 - US$6.68

OBS05 16mm round black obsidian beads strand wholesale
OBS05
The bead is black obsidian, A grades, round shape, 16mm, about 16 inches long, about 25 beads. The listed price is for one strand beads. Obsidian is v...

Start From: 5 Unit(s)
US$4.87 - US$5.72

OBS04 14mm round black obsidian beads strand wholesale
OBS04
The bead is black obsidian, A grades, round shape, 14mm, about 15 inches long, about 27 beads. The listed price is for one strand beads. Obsidian is v...

Start From: 5 Unit(s)
US$4.05 - US$4.77

OBS03 12mm round black obsidian beads strand wholesale
OBS03
The bead is black obsidian, A grades, round shape, 12mm, about 16 inches long, about 34 beads. The listed price is for one strand beads. Obsidian is v...

Start From: 5 Unit(s)
US$3.51 - US$4.13

OBS02 10mm round black obsidian beads strand wholesale
OBS02
The bead is black obsidian, A grades, round shape, 10mm, about 16 inches long, about 40 beads. The listed price is for one strand beads. Obsidian is v...

Start From: 5 Unit(s)
US$2.43 - US$2.86

OBS01 6mm round black obsidian beads strand wholesale
OBS01
The bead is black obsidian, A grades, round shape, 6mm, about 15 inches long, about 64 beads. The listed price is for one strand beads. Obsidian is vo...

Start From: 5 Unit(s)
US$1.62 - US$1.91