<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation . Materials that break in this way include quartz, flint, quartzite, jasper, and other fine - grained or amorphous materials with a composition of pure silica, such as obsidian and window glass . </P> <P> Conchoidal fractures can also occur in other materials under favorable circumstances . This material property was widely used in the Stone Age to make sharp tools, and minerals that fractured in this fashion were widely traded as a desirable raw material . </P>

Made out of brittle breaking rock materials such as flint chert and obsidian