Mother-of-pearl buttons, a biogenic precious gem.
Biogenic gemstones are gemstones of biological origin, created through natural biological processes rather than geological processes. Depending on the stone in question, some biogenic gemstones are completely biogenic, while others involve a mixture of natural and geological processes: gem-quality fossils, for example, are biogenic, but also mineral in nature. The value of biogenic gemstones varies considerably by gem and quality.
Coral is a biogenic precious gem.
Some well-known examples of biogenic gemstones include: pearl, coral, mother-of-pearl, and ivory. These precious materials are formed by a variety of organisms for a variety of purposes. Nacre, for example, is formed from the deposition of layers of a material called nacre, used to expand the shells of some marine molluscs, while ivory is a type of tooth present in elephants and rhinoceroses, among others.
Biogenic gemstones, like pearls, have biological origins.
Other biogenic gemstones, such as amber and ammolite, consist of fossilized remains of natural materials. In the case of amber, the material is the sap, which can also trap insects and other inclusions that make the resulting gem more biologically interesting. Ammolite is made from the remains of fossilized ammonites, marine mollusks that swam in the oceans millions of years ago. Some people refer to fossilized gemstones as minerals rather than biogenic gemstones, since geological processes are involved in their formation.
The appearance of biogenic gemstones varies widely, as you can see from the examples above. Some biogenic gemstones are translucent with blemishes and inclusions, like amber, while others are solid, like ivory. Colors can vary significantly, as can hardness. Some biogenic gems are extremely brittle and must be handled with care and carefully placed to ensure they do not crack, tarnish, or break, while others are tough enough to be used as billiard balls.
When evaluating the quality of biogenic gemstones, people should look for things like clarity, cut, and color, just like diamonds, and should also look for obvious cracks, flaking, or other signs of damage. For set gems, the setting must be firm and stable, and for fragile gems, it must be protected or the gems covered with hard glass to reduce the risk of loss or damage. There are also some ethical issues related to biogenic gemstones, like ivory, for example, which is particularly challenging from an ethical point of view due to the widespread poaching of elephants for their ivory. There are no certification programs to confirm the origins of biogenic gemstones for concerned consumers, which can make ethical purchasing difficult, and some people avoid controversial gemstones like coral and ivory for this reason.