Quiz: Remember the definition of mal de mer?


[tak-uh-lahyt] /ˈtæk əˌlaɪt/
noun, Petrography
a black, glassy form of basalt, readily fusible and of a high luster.
Also, tachylite.
1865-70; tachy- + -lyte2
Related forms
[tak-uh-lit-ik] /ˌtæk əˈlɪt ɪk/ (Show IPA),
adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source
British Dictionary definitions for tachylite


a black basaltic glass often found on the edges of intrusions of basalt
Derived Forms
tachylytic (ˌtækɪˈlɪtɪk), tachylitic, adjective
Word Origin
C19: from German Tachylit, from tachy- + Greek lutos soluble, melting, from luein to release; so called because it fuses easily when heated. The form tachylite is influenced by -lite stone
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Cite This Source
Encyclopedia Article for tachylite

glassy igneous rocks low in silica, such as basalt or diabase. Tachylytes are black with a pitchlike or resinous lustre; in thin sections they are characteristically brown and translucent, and the glass is crowded with granules of magnetite. Tachylytes are found only under conditions that imply rapid cooling, and they are much less common than are the corresponding acid volcanic glasses, principally because of the greater fluidity and greater tendency of basic lavas to crystallize.

Learn more about tachylite with a free trial on
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source

Word of the Day

Difficulty index for tachylyte

Few English speakers likely know this word

Word Value for tachylite

Scrabble Words With Friends

Nearby words for tachylite