珍珠的特有的光澤是光在這些透明的真珠質層上反射和衍射造成的，珍珠質層越薄越多，光澤就越漂亮。一些珍珠的螢光是由不同真珠層對入射光不斷的折射所形成的。一般的珍珠是白色的，有時有米黃色或粉色的光澤，也有些珍珠帶有黃色、綠色、藍色、棕色或黑色的顏色。黑珍珠因其鮮有而昂貴。珍珠主要是一些瓣鰓綱軟體動物的產物。這些動物特定的上皮細胞會分泌碳酸鈣，主要是由貝殼硬蛋白粘合在一起的文石和方解石。這種混合被稱為真珠質。珍珠的成因有：外套和甲殼的受傷，這時珍珠會作為傷口縫合分泌到傷口處。如果有寄生蟲或是上皮組織落到動物的內部[來源請求]。外物（如沙）是不會引起珍珠生成的[來源請求]。而人工珍珠注入的是由一層外來上皮包繞的真珠質核。這些動物分泌的珍珠形成有數月到年不等。大顆粒的珍珠形成對於該動物來說很可能是致命的。除使用珍珠蛤外還有使用鮑生產珍珠的方法。珍珠人工養殖的國家，在宋代就已經開始了珍珠的人工養殖。但是規模不大，世界上大規模進行人工養殖珍珠的是日本。日本的珍珠養殖發展相當迅速，中國從日本引進了幾個好的珍珠養殖品種。珍珠的價值主要由它的光澤、顏色、大小、有無表面的缺陷和形狀來決定。其中光澤最為重要。大的圓滿的珍珠比較罕見，一般被用在指戒上，水滴狀的一般用在懸掛物上，不規則的常用在項鍊中。A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of a clam, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes (baroque pearls) occur. The finest quality natural pearls have been highly valued as gemstones and objects of beautyfor many centuries. Because of this, pearl has become a metaphor for something rare, fine, admirable and valuable. Natural (or wild) pearls, formed without human intervention, are very rare. Many hundreds of pearl oysters or mussels must be gathered and opened, and thus killed, to find even one wild pearl; for many centuries, this was the only way pearls were obtained, and why pearls fetched such extraordinary prices in the past. Cultured pearls are formed in pearl farms luster of pearls depends upon the reflection, refraction, and diffraction of light from the translucent layers. The thinner and more numerous the layers in the pearl, the finer the luster. The iridescence that pearls display is caused by the overlapping of successive layers Freshwater pearls form in various species of freshwater mussels, family Unionidae, which live in lakes, rivers, ponds and other bodies of fresh water. These freshwater pearl mussels occur not only in hotter climates, but also in colder more temperate areas such as Scotland (where they are protected under law). Most freshwater cultured pearls 珍珠是一种古老的有机宝石。主要产在珍珠贝类和珠母贝 珍珠是一种古老的有机宝石。主要产在珍珠贝类和珠母贝