Foreign GRS certificates have detailed classification of emerald filling optimization oil injection. The amount of oil injected will be divided into seven grades: none, insignificant, secondary, medium, obvious and obvious.

It can be seen that the comment item is marked as "CE (O): unimportant", in which CE (O) is cleanliness optimization (oiling), and it is not important to refer to trace.

A minor is a small amount of oil, and then you don't sell it. If it's as small as medium oil, it's bigger.

NGTC certificate

The National Jewelry and Jade Quality Supervision and Inspection Center (NGTC) issued the international standard of emerald. According to relevant sources, according to the amount of oil injected, the national inspection commission will mark "cleanliness improved", "cleanliness slightly improved", "cleanliness moderately improved" and "cleanliness seriously improved" in the remarks.

GIA certificate

GIA is divided into none, F 1 (slight), F2 (moderate) and F3 (significant) according to the amount of oil injected by emeralds.

Colorless oil emeralds are determined according to the characteristics of cracks and defects in emeralds and the cutting methods of emeralds. Oil injection is the most effective means to protect emeralds, and it is also recognized by the international gem community as an optimization means that does not destroy their naturalness. If you are not a millionaire, it is an extreme idea and behavior to blindly pursue oil-free emeralds.