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- ''This article is about volcanic glass. For other uses see obsidian (disambiguation).
Obsidian is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth (see glass transition temperature). It is commonly found within the margins of felsic lava flows, where cooling is more rapid.
Origin and properties
While a rock like basalt is dark because of ferromagnesian enrichment, despite its dark color, obsidian consists mainly of SiO2 (silicon dioxide), 70% or more. Obsidian is mineral-like, but not a true mineral because it is not crystalline. Its composition is very similar to that of granite and rhyolite. It is sometimes classified as a mineraloid. 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. The breakdown of obsidian is accelerated by the presence of water. Tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, though few scientists now adhere to this hypothesis.While pure obsidian is always dark in appearance, the color varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black color. 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 obsidian) or rainbow sheen (rainbow obsidian). Obsidian is relatively soft with a typical hardness of 5 to 5.5. Its relative density is approximately 2.6.
More on [ Obsidian ]
Not much love for these AJ II White/Obsidian-Orange Blaze Retros, 2010 limited release, whats your take? http://bit.ly/874tnt
solecollector (SOLE COLLECTOR) Tue, 15 Dec 2009 03:30:41 -0000
Not much love for these AJ II White/Obsidian-Orange Blaze Retros, 2010 limited release, whats your take? http://bit.ly/874tnt <WWH>
Just noticed they made the Obsidian sword small... :(
AQWTrogdorV20X6 (Cody ) Tue, 15 Dec 2009 02:01:22 -0000
Just noticed they made the Obsidian sword small... :(
Silver Circle and Obsidian Cuff Bracelet-FREE SHIPPING - $95.00 This "chain" style silver circle and ... http://ow.ly/169Eou
Naked_Jewelry (Sally Jewett-Brocato) Tue, 15 Dec 2009 01:55:06 -0000
Silver Circle and Obsidian Cuff Bracelet-FREE SHIPPING - $95.00 This "chain" style silver circle and ... http://ow.ly/169Eou
Check out this Amazon #deal: 'Dell Inspiron Mini 1011 10.1-Inch Obsidian Black Netbook' http://bit.ly/6fCmpv
xemmy (xemmy) Tue, 15 Dec 2009 01:24:13 -0000
Check out this Amazon #deal: 'Dell Inspiron Mini 1011 10.1-Inch Obsidian Black Netbook' http://bit.ly/6fCmpv
Strength with softness shows in this American handcrafted Modern Obsidian Moonstone Sterling Cuff Bracelet http://bit.ly/5I3IRl
anothertime (Another Time Antique) Tue, 15 Dec 2009 00:47:18 -0000
Strength with softness shows in this American handcrafted Modern Obsidian Moonstone Sterling Cuff Bracelet http://bit.ly/5I3IRl
28" Snowflate Obsidian beaded necklace with Silver Leaf Jasper Drop - Free Shipping!! http://bit.ly/CEJDc
DaisyDirlDesign (Linda Kennedy) Tue, 15 Dec 2009 00:13:32 -0000
28" Snowflate Obsidian beaded necklace with Silver Leaf Jasper Drop - Free Shipping!! http://bit.ly/CEJDc
GameSpot - Offers review, demo, screen shots, hints and walkthroughs.
Meta Description: [ Obsidian for PC - GameSpot offers reviews, previews, cheats, and more. Count on us for all of the latest on the Obsidian Computer Game. ]
IMDb: Obsidian (1997) - Cast and crew data from Internet Movie Database.
Meta Description: [ Obsidian on IMDb: Movies, TV, Celebs, and more... ]
Obsidian Hint Guide - Comprehensive hint guide from Gamespot.
Meta Description: [ Video Games - GameSpot is the world's largest source for PC, PlayStation 2, Xbox, GameCube, PSP, DS, Wii, GBA, PS2, PS3, PlayStation 3, and Xbox 360 video game news, cheats, reviews and more! ]
Obsidian Realm, The - Information, hints, spoilers, and message board.
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