Coal煤
Coal can be considered to be a sedimentary rock in the class known as chemical sedimentary rocks. It is made up mostly of organic matter. Microscopic examination reveals plant matter - leaves, bark, wood. This plant matter has been compacted over a long time period. It is presumed to have its origin in plant matter that has been buried in an oxygen-deficient environment like a swamp and then compacted over time. 煤可以被看作是化学沉积岩的一种。它主要由有机物质组成。显微观察显示有植物物质——叶子、树皮、木材。这种植物物质在很长一段时间内被压实。它被认为起源于被埋藏在缺氧环境（如沼泽）中的植物物质，然后随着时间的推移被压实。
Lignite and bituminous coals are considered to be just sedimentary rocks, but anthracite coal is metamorphic. Anthracite has been altered by the pressures of folding and deformation during mountain building. 泥炭和烟煤被视为普通的沉积岩，但石墨煤是变质岩。石墨煤在造山运动过程中受到褶皱和形变的影响而发生改变。
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Index Reference Lutgens and Tarbuck Ch 6 索引 参考 Lutgens 和 Tarbuck 第6章 | ||
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