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Deformation series | Type of tectonically deformed coals | Texture and structure | Structural fracture and wrinkle | Breaking degree | Micro characteristics | Deformational mechanism and environment |
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Brittle deformation series | Cataclastic structure coal | Band texture could be seen; layer structure was preserved | Multidirectional fracture cuts; no obvious displacement | More hardness; crumbing is difficult | | |
Mortar structure coal | Little band texture was seen; lentoid structure was formed | Multidirectional fracture cuts; obvious displacement in the mortar | Broken into detritus from 1 to 5 cm; angular shape | Tensile fracture, shear fracture, and compressional fracture | Multi directional compression and extension; extension was the predominant role |
Granulitic structure coal | Primary structure not present; disorder of players | Multi directional cross fracture; particles were rotated | Broken into detritus, 1 cm |
Mealy structure coal | Primary structure not present; powdered particles formed | No obvious directions for the particles | Be pinched into powered particles | Strong compressional fracture zone or scaly structure coal be reconstructed later |
Schistose structure coal | Band texture could be seen; layer structure was preserved | Single directional fracture; little displacement on the surface | Broken into detritus from 1 to 5 cm, shard shape | Single directional compression and extension or shearing strain environment |
Thin-layer structure coal | Little band texture was seen; layer structure was not obvious | Single directional fracture; obvious displacement on the surface | Broken into detritus, 1 cm |
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Brittle-ductile series | Scaly structure coal | Primary structure not present; scaly structure was formed | Multi directional cross-fracture; coal was cut and wrinkled; the particles could be rotated | Broken into detritus, 0.5 cm; shard shape | Shear fracture, cleavages | Strong shearing or cleaving strain environment |
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Ductile deformation series | Wrinkle structure coal | Primary structure not present; wrinkle structure was formed | Coal was wrinkled | Broken into detritus, 0.5 cm, shard shape | Wrinkle, foliated coal, S-C structure, eyed structure, optical anisotropy structure and wavy extinction | |
Mylonitic structure coal | Primary structure not present; mylonitic structure was formed | The particles had directional arrangement; flow structure was formed | Was pinched into powered particles | Strong shearing or long and low stress deformation |
Ductile structure coal | Primary structure not present; lump and lentoid structures were formed | No obvious physical deformation | More hardness; crumbing was difficult | | Long and low stress creep; ductile flow at high temperatures |
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