Feature Gems & Gemology, Winter 2012, Volume 48, No. 4

Natural Pearls from Australian Pinctada Maxima

The fascinating and colorful history of natural pearling in Australian waters is presented, from the early six-man luggers to the large ships in modern fleets where pearl culture has been the focus for the past several decades. For the scientific investigation of this paper, the authors retrieved natural pearls from wild Pinctada maxima in Australian waters and recorded the various properties that might help to differentiate between natural pearls from this mollusk and those that are accidental by-products of the culturing process. Three distinct categories of host Pinctada maxima shells and mantle pearls were collected and examined by the authors: (1) from wild shell prior to any pearl culturing operation, (2) from wild shell after pearl culturing and approximately two years on the farm, and (3) from hatchery-reared shell prior to pearl culturing. Data were collected from microscopy, X-rays of internal structures, using real-time microradiography and X-ray computed microtomography, various forms of spectroscopy, and LA-ICP-MS chemical analysis. The results showed that microradiographic structures previously considered indicative of an accidentally cultured P. maxima pearl may not be conclusive, and that such criteria should only be applied with the utmost caution by an experienced technician.