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Weird Words: Conchoidal

Conchoidal is not only a weird geological term, it is also vitally important in terms of developments that led to human survival. In geology, conchoidal refers to a curved, shell-like shape that certain brittle rocks and minerals exhibit if fractured by a blow. As a result of the radiating shock created by a sharp blow, such fractures have smooth rounded concentric ridges that resemble a mussel shell with its growth lines. Indeed, the word “conchoidal” is derived from the Greek word konkhoeides, meaning “like a mussel”.

Conchoidal fracture in obsidian enabled stone-age cultures to produce arrowheads.
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Rock & Gem April 2019, WorkShops in the Wild : Lifelong Learning at Wildacres, Emergence of Flourescence, Bladed Barite : In the East Potrillo Mountains, And More....