Using microradiography to assess nacre thickness of mabé pearls: Technique suitability and insights

Abstract Nacre thickness is a major factor influencing the quality and value of half-pearls (‘mabe’), yet accurate determination of nacre thickness, in a non-destructive manner, is problematic. Microradiography is commonly used to measure the nacre thickness of round pearls, however the suitability of this technique for mabe has not previously been assessed. Mabe were cultured in winged pearl oysters ( Pteria penguin ) for periods of 200 to 380 days to produce pearls with a range of nacre thicknesses. The nacre thickness of each pearl was quantified using microradiography and standard micrometer techniques. A strong, significant relationship was observed between measurements obtained using both techniques ( R 2  = 0.88, P  ≤ 0.001). Microradiography produced defined, measureable images, with a resolution of ±0.04 mm, for mabe pearls with nacre thicknesses between 0.1 and 1.3 mm. Mabe nacre thickness and pearl quality were significantly influenced by the position of the pearl nucleus within the shell ( T (95)  = 7.14, P P