![Conch Pearl Ring. Conch Pearl Ring.](https://www.langantiques.com/university/wp-content/uploads/elementor/thumbs/Conch_Pearl-q88jzrj3s4crx3em3k8ws307d2fiv96qz8rl5fvzig.jpg)
Calcareous concretions are pearl-like growths produced in mollusks that lack nacre. While still composed of calcite and aragonite, the crystals are much coarser. Some of these “pearls” may have a flame-like sheen on their surface. Calcareous concretions seen in jewelry include Conch Pearls and Quahogs.