When we think about pearls, the nacreous ones that are produced by some bivalves come to our mind. But there are rare and beautiful pearls without the typical nacreous pearly luster. Conch pearls are great examples that typically form in the Queen Conch, a Caribbean gastropod currently known in the scientific community as Aliger gigas. It was formerly known as Strombus gigas and, more recently, also as Lobatus gigas (by the way, this frequent updates in taxonomy are not isolated cases for the gem community to acknowledge, as science is a dynamic beast!).
Conch pearls have porcellanous lustre and white to salmon to brown colour, but preferably pink, with a peculiar cross lamellar microstructure that causes a characteristic “flame structure” that adds to its desirability.
This species has been listed in CITES Appendix II since 1992, and it is mostly the seafood industry, not the pearl or jewellery industry, that is behind this listing (CITES Appendix II lists species that are not necessarily threatened now, but that may become so unless trade is controlled; they can be traded internationally for commercial purposes, but within strict regulations, requiring determinations of sustainability and legality, e.g. an export permit or re-export certificate).
Reportedly there is 1 gem-quality pearl in each 50,000 shells that are primarily fished for their meat.
In 2009 cultured conch pearls have been reported in scientific experiments at the Florida Atlantic University but with no commercial follow up has been reported so far.
In the photos, Marjorie Merriweather Post’s Cartier pendant brooch ca. 1922 © Hillwood Estate, Museum & Gardens ; Fine 4.80 ct conch pearl showing the flame structure © Bonhams ; Beautiful conch shell in the Bahamas © Queen Conch Lab | Universidade do Atlântico da Flórida, Harbor Branch Oceanographic Institute
Artigos convidados de Rui Galopim de Carvalho:
https://gem-spectrum.com/category/rui-galopim-de-carvalho
Sobre o autor:
Rui Galopim de Carvalho Rui é um renomado consultor independente em educação gemológica, autor, especialista em treinamento para a indústria de luxo e palestrante internacional popular sobre gemologia e história das gemas. Ao longo de seus 30 anos de experiência como gemólogo, Rui estudou importantes coleções em museus públicos e privados, notadamente as Joias da Coroa Portuguesa.
Fundador da popular série de webinars Home Gemmology, lançada durante o confinamento da COVID-19, Rui tem uma longa trajetória como comunicador na área da gemologia, principalmente nas redes sociais, onde é uma figura popular.
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