while searching through the Niles MI public library stacks for a difference reference book I ran across one I read years agoe that may be of interest to those who are seriously interested in gunflints.
TM Hamilton ,the well known authority on colonial era trade guns, had excellent and extensive connections in the North American historical archaeological and material studies community. As a result he was able to conduct a very detailed and in-depth analysis of the gunflints excavated at Fort Michillimackinac and a number of other colonial sites. His "dig-book" report, whihc he prepared with K. O. Emery was published by the Mackinac Island Park Commission's Archaeological Completion Report #13 in 1988 under the title "Eighteeth-Century Gunflints for Fort Michillimackinac and other Colonial Sites"
In it he compares both french, english, spanish, and German as well as some native american original flints by thin-section and x-ray petrographic analysis as well as spark array analysis when used in a flintlock. I 'd be interesting to see how his study dovetails with Larry Pletcher's work
I do not know if this book is available through the usual commercial sources, but it should be via interlibrary loan. It was published, privately printed, by the Park Commission and does not bear an ISBN number. I will do some further checking for potential sources and I will renew it and bring it down to Louisville on the 27th in case anyone wants to look at it.
I have found it listed in Amazon, but see also ABEBooks.com, also Bookseller.com and bookfinder.com it is not cheap by a long shot but a good reference for a serious researcher or student