One of the fun things about collecting gemstones is to be able to cut and or/polish the stones yourself.
To that end, there are a variety of instruments one can purchase.
Readers of this blog in America can purchase a rock tumbler from Amazon.com:
and if you want to learn how to cut opals and other gemstones, there are of course a few books on the subject:
Amazon.com UK also has a variety of products for sale: Rock tumbler and other material.
And of course, such material can be purchased at your local gemstone store, or via the various gemstone magazines.