Fig. 5
The characteristics of various patterns in transmitted-light microphotographs. a Fine-grained structure presented in the sample with original state; b Fine-grained structure presented in the sample with surface integrity damage; c Fine-grained sandy structure presented in the sample with surface color change; d Fine-grained structure presented in the sample with biological colonization (Qtz: quartz; Fsp: feldspar; Bt: Biotite; Calc: calcium)