A usually black or banded, hard volcanic glass that displays shiny, curved surfaces when fractured and is formed by rapid cooling of lava.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "obsidian" in a sentence
"Glass in the form of a volcanic residue such as obsidian is found in nature."
"Esparza explained to us that the colors in obsidian come from traces of different minerals embedded in it."
"I confess that I, too, had very little interest in obsidian until the day I walked into Don Eleno's obsidian workshop in the sleepy village of Navajas, located 30 kilometers southwest of Guadalajara."