Obsidian

Part of speech: noun

Pronunciation: /ˌɒbˈsɪd.i.ən/

Definitions

1. A dark volcanic glass formed when lava cools rapidly, typically black and smooth with sharp edges when broken
2. A lustrous volcanic rock composed of cooled lava that appears glassy and dark, prized for its razor-sharp fractured edges and use in tools and ornaments
3. A natural glass-like mineral substance created by rapid cooling of molten rock, characterized by its deep black coloration and keen cutting properties when fractured

Etymology: Pliny the Elder, the Roman writer, recorded a story about how the glass got its name. According to him, a man called Obsidius discovered the stone in Aethiopia, a region of Africa south of Egypt, and the material was named after him. The Latin adjective "obsidianus" was formed from that name, and English borrowed it as "obsidian" for the dark, glassy rock that forms when lava cools very quickly. The name's origin is a Roman attribution, and modern geologists do not treat Obsidius as a historical figure with any confirmed connection to the stone. What is clear is that the material was valued in antiquity: Roman and earlier cultures used it for blades and mirrors because it could be flaked to an edge sharper than many metal tools.

Synonyms: volcanic glass, igneous rock