Interfaces of microlayers, in most stalagmites from China, consist of opaqu
e and organic materials. Observed with microscope, the interfaces seem dark
under transmitted light and luminiferous under reflected fluorescent light
. Stalagmites in which the two optical characters are unified spatially wou
ld be most suitable for cross-dating use, and can play an important role in
the study on speleochronology and speleoclimatology.