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

• subconchoidal
  adjective
• conchoidally
  adverb

Etymology

Origin of conchoidal

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

Example Sentences

See Examples For:

conchoidal

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

Different beds, and even different parts of the same bed, presented specimens of the fibrous brown-coal, earth-coal, conchoidal brown-coal, and trapezoidal brown-coal of Jameson.

From Narrative of a Second Expedition to the Shores of the Polar Sea by John Franklin

Climbing the Rastrojito slopes, we sighted the Pedras Negras: these are huge travelled rocks of basalt, jet-black, breaking with a conchoidal fracture, and showing debris like onion-coats about their base.

From To the Gold Coast for Gold A Personal Narrative in Two Volumes.—Volume I by Sir Richard Francis Burton

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 Edward Hull