Mars Unique Jewelry Design
- Showcase and catalog of artisan jewelry crafted in fine metals and gemstones.
- http://www.jewelrybymars.com/

The Opal Association
- All about opals, includes miners, cutters, wholesalers, retailers, exporters, collectors, hobbyists, lapidaries.
- http://www.opal.asn.au

The Rock Tumbling Hobby Site
- Step by step guide, including tips on equipment and stone selection, preparation, and polishing.
- http://www.rocktumblinghobby.com/