Non Nacreous Pearls -Part One
The nacre is the combination of calcium carbonate (aragonite) and conchiolin. Secreted from a mollusc and layered together to form the nacre.
Some pearls do not have this nacre and are made of calcite and not aragonite. Technically speaking, these non-nacreous pearls are not actually pearls. They are classified as calcareous concretions and do still produce stunning gems and are very rare and highly expensive.
It has proven quite difficult to culture these types of “pearls” for any commercial value. Although it has been successful to culture some pearl varieties. These non-nacreous pearls are weaker in internal structure than nacreous pearls and prone to cracking.
They are still extremely valuable owing to their rarity, natural provenance and natural formation.
Varieties of Non-Nacreous Pearls
1. Gastropod Molluscs; including Conch pearls (strombus gigas) and Melo pearls.
Conch pearls are the product of a large marine snail- the queen conch. They are native to the Caribbean. Although known and prized for their deep pink colour, the pearls are found in orange, white, yellow, beige and brown. The conch pearl often displays a “flame” like structure or pattern making it more valuable and beautiful. Most conch pearls have an oblong or oval shape and spherical or near round specimens are very difficult to find.
Highly Prized Jewellery
Conch pearls are highly valuable and highly prized. Mikimoto has recently launched a collection of conch pearl jewellery. The conch pearl earrings above display two identical pearls.
The over- exploitation of the mollusc has led to a massive depletion of the queen conch pearl due to the modern fishing gear and industrial fishery. Therefore, in 1992 the strombus gigas has been included in Appendix 11 of the CITES. (Convention on International Trade in Endangered Species of Wild Fauna and Flora).
Culturing the Queen Conch
A method for culturing conch pearls has been developed very recently by scientists from Florida Atlantic University’s Harbour Branch Oceonographic Institute (HBOI). Drs Hector Acosta-Salmon and Megan Davis became the first and only group to develop a method to grow queen conch cultured pearls.
CITES (2003) AC 19 Doc Review of significant trade in specimens of Strombus gigas
Federman D. (2007): The pink pearl: A natural treasure of the Caribbean
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