obsidian

American  

[uhb-sid-ee-uhn] / 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.

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obsidian British  

/ ɒbˈsɪdɪən /

noun

1. Also called: Iceland agate.  a dark volcanic glass formed by very rapid solidification of lava

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obsidian Scientific  

/ ŏb-sĭd′ē-ən /

1. 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.

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Etymology

Origin of obsidian

First recorded in 1350–1400; from 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, from Latin

Example Sentences

Elordi strides naturally through the film’s burning-of-Atlanta orange sunscapes and its grasslands stabbed by obsidian spikes of rock.

From Los Angeles Times • Feb. 11, 2026

From precolonial Mexico we discover obsidian mirrors used for divination in Mayan and Aztec ceremonies.

From The Wall Street Journal • Jan. 16, 2026

Like obsidian, in fact, their edges are sharp but the shards have an almost twirly shape and lack the crystalline structure of black-colored minerals like augite or tourmaline.

From Salon • Mar. 4, 2025

One gem is thought to be a rare, 2nd Century head of the Greek hero Hercules made from obsidian, a type of volcanic glass.

From BBC • May 27, 2024

Black obsidian walls reflected the dim silver glow leaking out of a closed clamshell-like container atop a pedestal.

From "Tristan Strong Punches a Hole in the Sky" by Kwame Mbalia

Related Words

• sunless
• unlighted
• unlit