Amberis formed of tree resin exuded as a protective mechanism against disease and insect infestation①， then hashardened and been preserved in the earth’s crust for millions of years. Amber is often regarded as a gem②， in face， it is an organic substance③ whose structure has changed but little for long time. Its organic matter is replaced unlike that of other fossilized material， in which organic matter is replaced with minerals.
Because amber oxidizes④ and degrades when exposed to oxygen， it is preserved only under special conditions. Thus it is almost always found in dense， wet sediments⑤ ， such as clay and sand that formed at the bottom of an ancient lagoon⑥ or a river delta. While hundreds of amber deposits occur around the world， most of them contain only trace amounts of the substance； only about twenty deposits in the world containingamounts of amber canbe mined.
Amber has preserved ancient life to such infinitesimal⑦ detail that it even captures fragments of DNA of the organisms entrapped⑧ in it. Such a wide variety of creatureshas formed a unique⑨ scene in the world.
① Infestationn.(动、植物的)寄生虫侵扰
② gemn.宝石，宝玉
③ organic substance 有机物质
④ oxidizev.使氧化，使生锈
⑤ sedimentn.沉积，沉淀
⑥ lagoonn.咸水湖
⑦ infinitesimaladj. 极微小的，无限小的
⑧ entrapv. 欺骗，使陷入
⑨ uniqueadj. 唯一的，独一无二的，独特的[(+to)]
琥珀——通往过去的窗口
琥珀，是由树脂形成的，它从树脂中流出，作为一种抵御疾病和昆虫侵袭的保护机制，逐渐风蚀变硬，然后于地表中被保存数百万年。琥珀经常被认为是一种宝石，但事实上它是一种有机物质，其结构虽历经了无数岁月变迁，但改变的却很少，与其他的化石材料不同，琥珀的有机结构是由矿物质构成的。
琥珀暴露于氧气中容易氧化、退化，所以只能在特殊的条件对其进行保护。因此，它总是出现在稠密而潮湿的沉积地带，如在古代的盐碱地带和三角洲河流底部形成粘土、沙土中。数百种琥珀沉积在世界周围，但大多数也就只包含物质的蛛丝马迹，世界上仅有大约二十种的沉积物中含有相当数量的琥珀可供开采。
琥珀保护古代的生物已经到了如此细微的地步，以至于它可以捕捉一些陷入其中的物质的DNA片断。这样一种丰富多彩的生物，在世界上已经形成了一道独特的风景线。
