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[kong-koid-l] /kɒŋˈkɔɪd l/
adjective, Mineralogy
noting a shell-like fracture form produced on certain minerals by a blow.
Origin of conchoidal
1660-70; conchoid + -al1
Related forms
conchoidally, adverb
subconchoidal, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for conchoidal
  • When obsidian breaks it fractures with a distinct conchoidal fracture.
  • Highly silicified examples flake with a good conchoidal fracture.
  • The silt and clay commonly display blocky to conchoidal rock fracture.
  • It is opaque, with a golden metallic color and conchoidal fracture.
  • Using a polarizing microscope, crushed samples can be used to show the conchoidal fracture.
  • Typically, the clay is brittle and breaks with a conchoidal fracture.
  • The impact from one generated the other, leaving behind a conchoidal-shaped fracture on the lower release.
  • The rock breaks with a conchoidal fracture and emits a ringing sound when struck with a hammer.
  • Windblown material tends to have sharp edges, a conchoidal shape, and surface etching.
  • The fresh blocky shale displays conchoidal fractures but becomes fissile upon weathering.
British Dictionary definitions for conchoidal


(of the fracture of minerals and rocks) having smooth shell-shaped convex and concave surfaces
(of minerals and rocks, such as flint) having such a fracture
Derived Forms
conchoidally, adverb
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
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conchoidal in Science
Of or relating to a mineral or rock surface that is characterized by smooth, shell-like curves. Obsidian and quartz often have conchoidal fractures.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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