conchoidal

[kong-koid-l]

adjective

Mineralogy.

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

conchoidal

/ 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

conchoidal

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.

Other Word Forms

• conchoidally adverb
• subconchoidal adjective

Word History and Origins

Origin of conchoidal¹

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

Example Sentences

These include the ‘conchoidal’ flaking that leaves a distinctive percussion mark; the production of several flakes from a single core, and the use of specific patterns of flake removal.

Read more on Nature

Around the summit of Mount Tarn the ground is bare, but so covered with small decomposed fragments, that the solid rock only appears occasionally: it is very hard, and breaks with a conchoidal fracture: some of the specimens which we detached bore indistinct impressions of organic remains.

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The fracture of this stone has in all instances been found to be irregularly conchoidal, and on exposure to the atmosphere and subjection to fire it crumbled to pieces.

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The two legs of a hyperbolic branch may belong to different asymptotes, and in this case we have the forms which Newton 660 calls inscribed, circumscribed, ambigene, &c.; or they may belong to the same asymptote, and in this case we have the serpentine form, where the branch cuts the asymptote, so as to touch it at its two extremities on opposite sides, or the conchoidal form, where it touches the asymptote on the same side.

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It is of black colour; its fracture is conchoidal, and it has a lustrous surface.

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