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.
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.
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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