conchoidal

American  

[kong-koid-l] / kɒŋˈkɔɪd l /

adjective

Mineralogy.

1. noting a shell-like fracture form produced on certain minerals by a blow.

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conchoidal British  

/ kɒŋˈkɔɪdəl /

adjective

1. (of the fracture of minerals and rocks) having smooth shell-shaped convex and concave surfaces

2. (of minerals and rocks, such as flint) having such a fracture

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conchoidal Scientific  

/ kŏng-koid′l /

1. Of or relating to a mineral or rock surface that is characterized by smooth, shell-like curves. Obsidian and quartz often have conchoidal fractures.

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Other Word Forms

• conchoidally adverb
• subconchoidal adjective

Etymology

Origin of conchoidal

First recorded in 1660–70; conchoid + -al ¹

Example Sentences

Mineral fracture surfaces may be rough, uneven, or show a conchoidal fracture.

From Textbooks • Jan. 1, 2017

A conchoidal fracture has a smooth, curved surface like a shallow bowl or conch shell, often with curved ridges.

From Textbooks • Jan. 1, 2017

Words flunked: dioceses, cantatrice, Nabuchodonosor, a fortiori, conchoidal.

From Time Magazine Archive

It has a conchoidal fracture, various shades of colour from grey to black; and under the microscope is seen to contain crystallites or microliths, often beautifully arranged in stellate or feathery groups.

From Volcanoes: Past and Present by Hull, Edward

The twigs soon become encrusted with a mammelated substance of a red colour more or less deep, nearly transparent, hard, and having a brilliant conchoidal fracture.

From Field's Chromatography or Treatise on Colours and Pigments as Used by Artists by Salter, Thomas