Calcareous Concretions

While the non-nacreous pearl in this three-stone diamond ring has a round shape like a classic true pearl, it also shows a faint, flame-like structure on its surface. This effect is due to the arrangement of aragonite in non-nacreous pearls and isn't found in true, nacre-bearing pearls. Photo courtesy of liveauctioneers.com and Fellows.

Article: Calcareous Concretions Value, Price, and Jewelry Information

Credit: Fellows