They are even added to our food. Table salt is a mineral. Salt is so essential, it was once used as money. Join a rock club. Clubs have field trips to look for rocks and minerals.
Members also swap and sell minerals among themselves.
Check out the World Wide Web. There are several sites now offering rock and mineral specimens for sale. Of course, it is also great to read and learn all you can. That way you will know the difference in poor quality and high quality specimens of the same mineral. Many people would assume that a tree is worthless once it dies.