Boulder opal is especially good to hand-carve into animals, as is strong ironstone with veins of opal colour. Black opal is expensive so black-opal animal carvings are rare. Opal animal carvings are popular among collectors.
Craftspeople can obtain a good polish or even hand-etched finish on animals like elephants, alligators, horses or turtles. Asian professional carvers, especially those who have worked with jade, make exquisite opal carvings.
Source your opal carvings direct from opal wholesalers and/or opal jewelry manufactures and carvers.