Many people believe that material that is organic (grown, rather than forged or machined) — is far healthier than anything artificial, when making jewelry. The rough and porous texture seems to allow the skin to breathe, and wearing organic jewelry in piercings tends to help promote a thicker-skinned, healthier, and less "funky" fistula.
Organic jewelry can be made from a variety of:
Organic jewelry is often more fragile than metal jewelry; heat especially can lead to cracking, weakening, or warping. In addition, the porous nature of the materials makes them very sensitive to chemicals and can even trap bacteria, leading to recurring infections (note that this is very uncommon).
The ethics of using some sorts of organic jewelry are also a concern. Many of the best hardwoods for jewelry, such as ebony, are endangered. Ivory, bone, and tusk, in particular, should be investigated fully to determine that it was obtained legally and ethically.