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Obsidian was used to inscribe the Rongorongo glyphs.
Obsidian can be used to make extremely sharp knives, and obsidian blades are a type of glass knife made using naturally occurring obsidian instead of manufactured glass.
Pre-Columbian Mesoamericans' use of obsidian was extensive and sophisticated; including carved and worked obsidian for tools and decorative objects.
Mesoamericans also made a type of sword with obsidian blades mounted in a wooden body.
Obsidian is used by some surgeons for scalpel blades, although this is not approved by the US Food and Drug Administration (FDA) for use on humans.
Well-crafted obsidian blades, as with any glass knife, can have a cutting edge many times sharper than high-quality steel surgical scalpels, the cutting edge of the blade being only about 3 nanometers thick.
Obsidian cores and blades were traded great distances inland from the coast.
Iron and other transition elements may give the obsidian a dark 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).
Obsidian may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled.
Obsidian has also been found in Gilat, a site in the western Negev in Israel.
Eight obsidian artifacts dating to the Chalcolithic Age found at this site were traced to obsidian sources in Anatolia.
The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth.