If you teach rocks then you teach minerals, right? Here is a nice little site devoted to the minerals of Oklahoma. It even has a county-by-county list of what and where you can find in each county. You will need to know how to read legal descriptions though. It’s only a few pages long and like many things on the internet you might want to just print it out. There are also some good links and other information for rock and mineral collectors.
http://www.brightok.net/~rockman/index.htm is the mineral site.
http://homestead.org/NeilShelton/Legals/HowToReadLandDescriptions.htm is a site you can use to teach (or learn) how to read the legal descriptions.