If you want to collect rocks and minerals just for the sake of
having them, you can buy specimens. Many can be purchased for
25 cents to $1 each, while a rare specimen can cost hundreds of
dollars.
The true pleasure is in finding your own samples. Later, when you
have a good-sized collection, you can fill gaps by buying specimens
or swapping extras with other collectors. You'll be amazed at the
number of amateur collectors. Perhaps no branch of science owes more
to the work of amateurs than mineralogy. Our great collection of
minerals in the U.S. National Museum in Washington, D.C., was
gathered almost entirely by two amateurs who devoted many years
and much money to their hobby.