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Of, relating to, or being a surface characterized by smooth, shell-like convexities and concavities, as on fractured obsidian.

[From Greek konkhoeidēs, mussellike : konkho-, concho- + -oeidēs, -oid.]

con·choi′dal·ly adv.


1. (Geological Science) (of the fracture of minerals and rocks) having smooth shell-shaped convex and concave surfaces
2. (Geological Science) (of minerals and rocks, such as flint) having such a fracture
conˈchoidally adv


(kɒŋˈkɔɪd l)

denoting a fracture shape whose surface resembles the inside of a clamshell, characteristic of certain minerals.
con•choi′dal•ly, adv.
References in periodicals archive ?
The reason for natural corundum being particularly suitable for grinding is its prominent basal cleavage that causes the crystal to break readily with a smooth flat surface at right angles to the axis of elongation through successive reductions in size unlike synthetic corundum (alumina), which has a conchoidal fracture.
The best quality were deemed to be of French or English origin, translucent with a smooth surface of a "uniform tint of light yellow or brown color, and slightly conchoidal fracture.
There is also misunderstanding of the term conchoidal fracture, which is an intrinsic property of some rocks, not a technique of knapping as suggested in some chapters.