KevininColorado: It's one of the secrets of our business. Some of the best (reliable, factual, and inexpensive if not free and downloadable!) information is available from state agencies. I'm sure, for example, Colorado has a department of mines and geology (or similar name). I haven't looked in a number of years. Here's another thing. For example, both Arizona and New Mexico have excellent such agencies. No reason in the world 90+% of the technical information available from them can be used in every Western state - and most states in the Union. Gold maps from the turn of the century through the 1930s are just as useful as those published this year. The earth hasn't changed that much in a hundred or two hundred years. Now, land use has certainly changed. Permission must be obtained from current owners, as required. But the geology is the same and there are some excellent publications from the 1920's and 1930's that are quite useful today. Good luck to all, ~The Old Bookaroo