Instructions
Visit your nearest rock shop or gem and mineral dealer. Many cabochons are cut from gemstones and minerals, such as malachite, opal, turquoise, onyx, tiger eye, quartz and agate. These are often either in displays about the particular stone, or in small, shallow bowls containing a variety of numerous types.
Attend a gem fair or rock show. Individuals and rock hounding groups may have semi-annual or annual events in your vicinity. Contact the local rock hound organization or a mineralogy group to inquire about local and regional shows. You can find all types of cabochons and sometimes will be able to watch as a lapidary artist cuts or polishes them.
Visit antique and vintage shops for vintage cabochons. You may find jewelry that contains the perfect stone. Check out your nearby craft shops as well--sometimes they will carry a selection of cabochons. Note, however, that these aren't commonly of the quality and variety you'll find at rock shops or gem fairs. The "glass pearls" (which come in a variety of colors) are considered cabochons too, even though they are actual glass and not gemstones.
Drop in at the largest bead store you can find. Many of these carry a range of cabochons suitable for jewelry making. Although you may easily be distracted by the millions (literally) of beads in such a shop, you can also inquire of the owner or manager about specific stones you hope to find.
Select the stones that appeal to you most when you do find them at any of these possible places. Choose according to color, interesting lines, the quality and smoothness. Rub them between your fingers to make sure there are no scratches or hard-to-see hairline cracks.