Go to your nearest university, find the main office of the department of geology, and explain our hobby and your interest in obtaining chert. They will put you in touch with a professor of geology who's job it is to be familiar with the sediment
If you collect arrow heads you will have found a ton of broken ones along the way, broken ones often make great gun flints. This one sparked like crazy, I trimmed the width a little to fit my lock jaws.
View attachment 280819
ary layers and outcroppings in the lands of your state. He, or she will be able to tell you. And a large proportion of geology phds are interested in this kind of stuff.
While you are at it, drop by the archeology department. And try not to get them started on indian history and artifacts. They might not let you ever leave. Especially once they find out you actually have a flintlock and are interested in the history of the land around you. Good way to make a new friend or two, and a good friend or two to have...