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obsidian

[uh b-sid-ee-uh n] /əbˈsɪd i ən/
noun
1.
a volcanic glass similar in composition to granite, usually dark but transparent in thin pieces, and having a good conchoidal fracture.
Origin of obsidian
1350-1400
1350-1400; < Latin Obsidiānus, printer's error for Obsiānus pertaining to Obsius, the discoverer (according to Pliny) of a similar mineral in Ethiopia; replacing Middle English obsianus < Latin; see -an
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Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for obsidian

obsidian

/ɒbˈsɪdɪən/
noun
1.
a dark volcanic glass formed by very rapid solidification of lava Also called Iceland agate
Word Origin
C17: from Latin obsidiānus, erroneous transcription of obsiānus (lapis) (stone of) Obsius, the name (in Pliny) of the discoverer of a stone resembling obsidian
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for obsidian
n.

"dark, hard volcanic rock," 1650s, from Latin obsidianus, misprint of Obsianus (lapis) "(stone) of Obsius," name of a Roman alleged by Pliny to have found this rock in Ethiopia.

Online Etymology Dictionary, © 2010 Douglas Harper
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obsidian in Science
obsidian
  (ŏb-sĭd'ē-ən)   
A shiny, usually black, volcanic glass. Obsidian forms above ground from lava that is similar in composition to the magma from which granite forms underground, but cools so quickly that minerals do not have a chance to form within it.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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