PEARL REPORT | 32 | 2022-2023 INNOVATION GIA’s 投入GIA的珍珠专业领域 | Bernardette Sto. Domingo 杜明高 | Backed by decades of know-how and experience in the pearl trade, GIA is reinforcing its reputation as the authority on pearl identification and grading. GIA美国宝石研究院在珍珠业累积数十年专业知识，堪称珍珠鉴定和分级的权威机构。 pearl expertise Diving into Ever committed to studying the science behind the pearl’s beauty, the Gemological Institute of America (GIA) has pursued pearl knowledge and research since 1949. Over the decades, it has built a solid standing in the field of pearl testing, making it the go-to institute for traders, auction houses, museums and collectors to examine rare specimens, including the Empress Eugenie pearls and the Saffron Dragon melo pearl. GIA also issues world-renowned pearl reports. Identifying pearls Natural pearls form when a foreign “intruder” irritates the mantle of a mollusc. The mollusc secretes calcium carbonate, often as nacre, to protect itself from the irritant. A pearl forms as the mollusc deposits more and more layers. “Natural pearls are rare. Roughly one in 10,000 molluscs will produce a pearl and of those produced, most are small and irregular in shape,” explained GIA. “Large natural pearls that are round or drop-shaped are incredibly valuable.” Many of these pearls, such as La Peregrina or the Baroda pearls, were owned by royalty and carry significant historical value. In 1917, millionaire Morton Plant famously traded his Fifth Avenue mansion for a double strand of natural pearls by Cartier. By comparison, cultured pearls form through human intervention when a nucleus is inserted into a mollusc to spur pearl growth. The nucleus is often a round shell bead, which determines the pearl’s size and shape. The most common cultured nacreous pearls are South Sea, Tahitian, Akoya and freshwater. Each pearl forms in a different type of mollusc and has distinct characteristics. Telling natural and cultured pearls apart often requires testing in a gemmological laboratory with sophisticated instruments. GIA scientists identify pearls by using X-ray techniques such as real-time microradiography (RTX) and X-ray computed microtomography (μ-CT) to analyse a pearl’s internal structure. Nacreous pearls are the most popular type in the market, but natural non-nacreous pearls such as melo and conch are also rare and highly treasured. Pearls symbolise perfection because they emerge fully formed frommolluscs and do not require faceting, according to GIA GIA指出，珍珠从软体动物生成时已完全成形， 不需要额外进行切割，是完美无瑕的象征
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