Optical coherence tomography (OCT) has been utilized to evaluate pearls including their nuclei noninvasively. By visualizing the internal structure of a pearl, we could measure the thickness of its nacre layer, observe the fine sub-structure of the nacre, and inspect the nucleus through the nacre. The system also allowed us to classify pearls into beaded- and non-beaded ones; usually, the saltwater ones have nuclei even though there are beaded freshwater pears and non-beaded saltwater pearls. Any cracks, crevices, or blemishes not only in the nacre but in the nucleus of a pearl could be clearly visualized. The OCT system was based on a 20 kHz swept-source of a 1.31μm central wavelength and an 110 nm full-width-at-half-maximum (FWHM) bandwidth. To get the 2-D images all around the circumference of a pearl, the pearl was rotated by a motorized rotating stage. And to achieve 3-D volume images, galvano-scans were made along two axes. Of all things, the OCT allowed us to check the use of a forbidden nucleus, usually made of a Giant Clam shell thus fragile, without hurting the pearl. With this modality, we believe, it would be possible evaluating pearls both in qualitative and quantitative. Comparison with the images taken with an optical microscope and X-ray radiograph gives the refractive index of pearl as about 1.53 in average.

© 2010 OSA

1. R. Y. Park, Y. C. Kim, and P. C. Kim, “The comparative analyses of akoya pearls using the bio-bead nucleus and bead nucleus made from washboard shell,” J. Korean Gems and Jewelry 1, 23–25 (2007).
2. J. Y. Kim, Korea Pearl Laboratory, 141–1 Bongik-dong, Jongno-gu, Seoul 110–390, Korea (personal communication, 2009).
3. H. C. Song, G. Xiang, L. Su, and Y. Fan, “Fluorescence spectrum analysis of freshwater pipless pearl,” J. Fishery Sci. China 5, 1–5 (1998).
4. Zh. Song, Xh. Yu, and Xh. Zhang, “Analysis on various factors influencing the quality of cultured pearl,” J. Gemol. 3, 18–21 (2001).
5. G. S. Zhang, X. D. Xie, S. Q. Qi, and P. C. Hu, “X-ray diffraction study of nacre in shell of hyriopsis cumingii (LEA),” J. Miner. Petrol. 22, 8–11 (2002).
6. U. Wehrmeister, H. Goetz, D. E. Jacob, A. Soldati, W. Xu, H. Duschner, and W. Hofmeister, “Visualization of the internal structures of cultured pearls by computerized X-ray microtomography,” J. Geol. 31, 15–21 (2008).
7. N. Zeng, Y. He, and H. Ma, “Application of optical coherence tomography in nacre identification and characterization,” Microw. Opt. Technol. Lett. 50(2), 442–445 (2008). [CrossRef]
8. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical coherence tomography,” Science 254(5035), 1178–1181 (1991). [CrossRef] [PubMed]
9. Y. Yasuno, V. D. Madjarova, S. Makita, M. Akiba, A. Morosawa, C. Chong, T. Sakai, K.-P. Chan, M. Itoh, and T. Yatagai, “Three-dimensional and high-speed swept-source optical coherence tomography for in vivo investigation of human anterior eye segments,” Opt. Express 13(26), 10652–10664 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-26-10652 . [CrossRef] [PubMed]
10. K. Wada, “Science of the pearl; formation and grading,” 2nd ed., publish a newspaper of pearl, Japan, 254–255 (1999).
11. http://www.cites.org/eng/resources/pub/checklist08/Checklist.pdf
12. http://www.iucnredlist.org/apps/redlist/details/22137/0
13. http://www.pearl-guide.com/forum/cultured-pearls/20-illegal-use-giant-clam-nuclei.html
14. K. T. Wada and A. Komaru, “Color and weight of pearl produced by grafting the mantle tissue from a selected population for white shell color of the Japanese pearl oyster pinctada fucata martensii (Dunker),” Aquaculture 142(1-2), 25–32 (1996). [CrossRef]
15. K. Wada, “The relation between the crystalline structure of the cultured pearls and elongation of the transplants mantle tissue in the process of pearl-sac formation,” Bull. Jap. Soc. Sci. Fish. 14, 549 (1960). [CrossRef]
16. K. Wada, “Science of the pearl; formation and grading,” 2nd ed., publish a newspaper of pearl, Japan, 248 (1999).

Aquaculture

• K. T. Wada and A. Komaru, “Color and weight of pearl produced by grafting the mantle tissue from a selected population for white shell color of the Japanese pearl oyster pinctada fucata martensii (Dunker),” Aquaculture 142(1-2), 25–32 (1996). [CrossRef]

Bull. Jap. Soc. Sci. Fish.

• K. Wada, “The relation between the crystalline structure of the cultured pearls and elongation of the transplants mantle tissue in the process of pearl-sac formation,” Bull. Jap. Soc. Sci. Fish. 14, 549 (1960). [CrossRef]

J. Fishery Sci. China

• H. C. Song, G. Xiang, L. Su, and Y. Fan, “Fluorescence spectrum analysis of freshwater pipless pearl,” J. Fishery Sci. China 5, 1–5 (1998).

J. Gemol.

• Zh. Song, Xh. Yu, and Xh. Zhang, “Analysis on various factors influencing the quality of cultured pearl,” J. Gemol. 3, 18–21 (2001).

J. Geol.

• U. Wehrmeister, H. Goetz, D. E. Jacob, A. Soldati, W. Xu, H. Duschner, and W. Hofmeister, “Visualization of the internal structures of cultured pearls by computerized X-ray microtomography,” J. Geol. 31, 15–21 (2008).

J. Korean Gems and Jewelry

• R. Y. Park, Y. C. Kim, and P. C. Kim, “The comparative analyses of akoya pearls using the bio-bead nucleus and bead nucleus made from washboard shell,” J. Korean Gems and Jewelry 1, 23–25 (2007).

J. Miner. Petrol.

• G. S. Zhang, X. D. Xie, S. Q. Qi, and P. C. Hu, “X-ray diffraction study of nacre in shell of hyriopsis cumingii (LEA),” J. Miner. Petrol. 22, 8–11 (2002).

Microw. Opt. Technol. Lett.

• N. Zeng, Y. He, and H. Ma, “Application of optical coherence tomography in nacre identification and characterization,” Microw. Opt. Technol. Lett. 50(2), 442–445 (2008). [CrossRef]

Opt. Express

• Y. Yasuno, V. D. Madjarova, S. Makita, M. Akiba, A. Morosawa, C. Chong, T. Sakai, K.-P. Chan, M. Itoh, and T. Yatagai, “Three-dimensional and high-speed swept-source optical coherence tomography for in vivo investigation of human anterior eye segments,” Opt. Express 13(26), 10652–10664 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-26-10652 . [CrossRef] [PubMed]

Science

• D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical coherence tomography,” Science 254(5035), 1178–1181 (1991). [CrossRef] [PubMed]

Other

• K. Wada, “Science of the pearl; formation and grading,” 2nd ed., publish a newspaper of pearl, Japan, 248 (1999).
• K. Wada, “Science of the pearl; formation and grading,” 2nd ed., publish a newspaper of pearl, Japan, 254–255 (1999).
• http://www.cites.org/eng/resources/pub/checklist08/Checklist.pdf
• http://www.iucnredlist.org/apps/redlist/details/22137/0
• http://www.pearl-guide.com/forum/cultured-pearls/20-illegal-use-giant-clam-nuclei.html
• J. Y. Kim, Korea Pearl Laboratory, 141–1 Bongik-dong, Jongno-gu, Seoul 110–390, Korea (personal communication, 2009).

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