The sardonyx, quartz family multilayered agate, doesn't come in cabochons, ready for you to make cameos.
You must look for a rough material at gem shows in your area or come to famous Tuscon Arizona Gem show.
I personally started to carve cameos in the 1970s using sea shells at first. The best seashell are from the Mediterranean. It has reddish brown background from the inside with white layer on the outside. Once you have found right material you will need diamond tools and so on. Good luck if you don't mind to get dirty.
Alec Stromberg, 1st place winner of 2011 Gemmys award of lapidary magazine Los Angeles California www.strombergtime.com
