煤类的划分一般是取样化验。

The division of coal species is based generally on the sampling and analysis.

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残植煤类仅出现在初始世代和中期世代的早期阶段。

Liptobiolites occur only in the primary generation and in the early stage of the middle generation.

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对于煤层结构复杂、变质程度较高的煤类，定性分类较为复杂。

As to the coal seams with complex texture and higher degree of metamorphism, the qualitative division of coal species is more complex.

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