Reference to almost any two text books in geology will show that there are different usages for the terms flint and chert. Perhaps much of the confusion is due to the fact that the origin of these substances is unknown, in which case exact definition at this time would be premature. Whatever the reason it seems advisable to bring out the variability of definition, if for no other purpose than to state a problem without attempting its solution. Blackwelder & Barrows- Elements of Geology, 1911, page 39. Flint is defined as "a very compact, dark grey, siliceous rock." Farther on, chert is said to be "an impure flint, usually of light color;" both occur in limestones.
Proceedings of the Iowa Academy of Science
©1920 Iowa Academy of Science, Inc.
Glock, Waldo S.
"The Use of the Terms Flint and Chert,"
Proceedings of the Iowa Academy of Science, 27(1), 167-173.
Available at: https://scholarworks.uni.edu/pias/vol27/iss1/21