clast
noun
ˈklast 
: a fragment of rock
Example Sentences
Recent Examples on the Web In geology, a clast is a fragment of an older rock, now broken up and embedded in a younger one. 
Richard A. Lovett, Outside Online, 16 Nov. 2020 Most of the rock fragments, or clasts, are dark in color, according to Michael Greshko at National Geographic, resembling lunar material. Jay Bennett, Smithsonian, 28 Jan. 2019 There is a lot of great information on the eruption on a website hosted by the University of Tokyo (Japanese – try Google Translate) that has compositional data and images of clasts from the eruption – Erik Klemetti, WIRED, 31 Jan. 2011 Researchers believe that the serpentine found in the clasts could form at depths of up to 12.5 miles down, where the subducting slab lies below the volcano. Jason Daley, Smithsonian, 18 Apr. 2017
Richard A. Lovett, Outside Online, 16 Nov. 2020 Most of the rock fragments, or clasts, are dark in color, according to Michael Greshko at National Geographic, resembling lunar material. Jay Bennett, Smithsonian, 28 Jan. 2019 There is a lot of great information on the eruption on a website hosted by the University of Tokyo (Japanese – try Google Translate) that has compositional data and images of clasts from the eruption – Erik Klemetti, WIRED, 31 Jan. 2011 Researchers believe that the serpentine found in the clasts could form at depths of up to 12.5 miles down, where the subducting slab lies below the volcano. Jason Daley, Smithsonian, 18 Apr. 2017 Word History
Etymology
Greek klastos broken, from klan to break; perhaps akin to Latin clades disaster
First Known Use
1952, in the meaning defined above