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Pearls have long been prized by wealthy people and were once considered more valuable than diamonds. They form when a mollusc coats an irritant with layers of nacre. Natural pearls develop around naturally occurring irritants, while cultured pearls form after a small nucleus is surgically implanted. Both can become beautiful and durable if enough nacre builds up around the nucleus.
珍珠长久以来备受富人珍视，曾经一度被认为比钻石还要贵重。软体动物将刺激物一层层包裹上珍珠质，珍珠就此形成。天然珍珠围绕天然产生的刺激物长成，而养殖珍珠则是在人工植入微小珠核之后形成。只要珠核外围积累足够厚的珍珠质，这两类珍珠都可以变得美观且经久耐用。
Pearls come from saltwater and freshwater sources, and their value depends more on individual qualities than on where they are found. Cultured pearls can be produced using different techniques, but cultivation takes years and many oysters do not survive or produce jewellery-quality pearls. Imitation pearls, often made by coating beads with a substance derived from fish scales, are less durable and can be distinguished from real pearls by their smooth feel compared with the gritty layers of nacre.
珍珠分为海水珠与淡水珠，其价值更多取决于本身特质，而非出产地点。养殖珍珠可以通过多种技术培育，但培育周期长达数年，而且很多牡蛎无法存活，或是产出达不到珠宝级别的珍珠。仿珠一般是在珠子外层涂上取自鱼鳞的涂层，耐用性较差；真珍珠摸起来有磨砂颗粒感，而仿珠表面顺滑，凭这个触感就能把二者区分开。
Pearls are assessed by their size, shape, colour, surface quality, and lustre. Natural pearls are generally the rarest and most valuable, followed by cultured pearls, while imitation pearls have little value. Gem laboratories can use X-rays to distinguish natural from cultured pearls. Historically, the Persian Gulf—especially Bahrain—was renowned for natural pearls, but oil pollution damaged the industry in the 1930s. Many natural pearls now held in India originally came from Bahrain.
珍珠的评判标准包括尺寸、形状、颜色、表面品相以及光泽。天然珍珠通常最为稀有、价值最高，其次是养殖珍珠，仿珠价值很低。宝石实验室可以借助 X 光区分天然珍珠和养殖珍珠。历史上，波斯湾（尤其是巴林）以天然珍珠闻名，但石油污染在 20 世纪 30 年代重创了当地珍珠产业。如今印度收藏的许多天然珍珠，原产地其实是巴林。
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