- José H. Leal
After the successful Conchologists of America 2022 in Galveston, Texas (see below), National Shell Museum’s Executive Director Sam Ankerson and I had the opportunity to visit the Houston Museum of Natural Science (HMNS). The goal was to explore the recently completed Strake Hall of Malacology and visit with Curator of Malacology Tina Petway. One of the displays that caught my eye was dedicated to pearls and the mollusks that make them, with remarkable examples of pearls made by well-known or common mollusks, and still, ones we never think of as capable of producing of those attractive gems.
The "Pearls and Host Shells" exhibit displays pearl-shell pairs, and it was great to see pearls made by a Horse Conch (Triplofusus giganteus), Queen Conch (Aliger gigas), Horned Helmet (Cassis cornuta), Giant Clams (Tridacna and Hippopus species), abalone (Haliotis species), Melo Volute (Melo melo), and others. One of the take-away messages from the exhibit is that, at least in theory, any mollusk with an external shell may produce a pearl, as long as a particle or small object ends up between the shell and the area of the animal’s mantle that deposits shell material onto the inner surface of the shell. The mollusk may envelop that foreign body or particle with shell material, provided it is located in an area where the animal will normally lay shell material. If the mollusk species has an internal layer consisting of nacre, or mother of pearl, then its pearl will have the “pearly”, iridescent look for which pearls are famous. If the mollusk doesn’t lay nacre, the resulting pearl will be plain-looking, non-iridescent, taking the color of the internal layer of the mother mollusk. A Horse Conch pearl will have the yellowish, non-iridescent color seen on the inside of the Horse Conch shell, a Queen Conch pearl will have the salmon-pink color of the internal layer of a Queen Conch, and so on.