Marc–
I think you will have to do the legwork yourself to figure out if you own the minerals. When I needed to figure out some mineral acres in Roosevelt County, I went to the county courthouse, and spent an 8-hour day elbow-to-elbow with landmen going through the books. The county clerk will not do the work for you, but he/she will show you what books to go through. It can be a long slog following this stuff out if parts of your property have been sold over the years.
You will need to have the legal description to follow it out.