The first known archaeological evidence of usage was in Kariandusi and other sites of the Acheulian age (beginning 1.5 million years BP) dated 700,000 BC, although the number of objects found at these sites were very low relative to the Neolithic.
Obsidian was valued in Stone Age cultures because, like flint, it could be fractured to produce sharp blades or arrowheads.
This breakdown of obsidian is accelerated by the presence of water.
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.
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.
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.
These bubbles can produce interesting effects such as a golden sheen (sheen obsidian).
This is the case in Yaxchilán, a Maya city where even warfare implications have been studied linked with obsidian use and its debris.
Pre-Columbian Mesoamericans' use of obsidian was extensive and sophisticated; including carved and worked obsidian for tools and decorative objects.
The translation into English of Natural History written by Pliny the Elder of Rome shows a few sentences on the subject of a volcanic glass called obsidian (lapis obsidianus), discovered in Ethiopia by Obsidius, a Roman explorer. Crystalline rocks with obsidian's composition include granite and rhyolite.
Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline; in addition, its composition is too variable to be classified as a mineral. 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.
Obsidian cores and blades were traded great distances inland from the coast.
Obsidian was used to inscribe the Rongorongo glyphs.
"Apache tears" are small rounded obsidian nuggets often embedded within a grayish-white perlite matrix.