General information of jade
Overview of Xiu jade(Xiuyan Jade)
Distinguish quality jade from fake or inferior jade
Jade's grading system in common language

A Grade: 100% all natural desirable color, texture, and watery luster. Not all natural jade can be graded as A Grade, and neither can all the 100% natural jade to be priced as A Grade. For a piece of jade to be graded and priced as A Grade, it must have all the above mentioned qualities.

B Grade: Synthetically enhanced, most of the time from natural coloration, but acid treated for better translucency. The color may or may not fade over time. Mineral impurities bleached out.

C Grade: Dyed color, mostly from outside. Color will fade within 5-6 years.

From: LuMingTang