obsidian
ob-SID-ee-un
Volcanic glass — magma that cooled so rapidly it had no time to form crystals, solidifying instead into a smooth, glassy, usually black or dark-brown rock with a conchoidal fracture that produces edges sharper than surgical steel. Obsidian has been used for cutting tools and weapons for at least 700,000 years, and obsidian blades are still used in some microsurgical procedures because their edges are thinner and smoother than any metal scalpel. It is rock at its most refined — all substance, no structure, pure material.
Etymology
Latin obsidianus lapis, possibly a corruption of obsianus, after Obsius, a Roman who supposedly discovered a similar stone in Ethiopia (according to Pliny the Elder). The attribution may be apocryphal, but the stone is real.
Notes
Obsidian source identification — matching a tool to its quarry by chemical fingerprint — has been used by archaeologists to trace trade networks spanning thousands of miles and thousands of years.
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