Of course the officials would not record the lucky or unlucky elements of the emperor. It must be held with highest confidentiality and strictest secrecy.
We can however, deduce it through three events that happened:
First, he is called Emperor Qian Long. "Qian" is one of the eight hexagram of I-Ching. It belongs to the element of metal, the element colour being white. "Long" means a big lump, or in abundance. "Qian Long" can be literary be translated to mean "in abundance of the great metal element". Would he be called "Qian Long" if metal, white in its element colour, was not his lucky element?
Secondly, it was recorded that when Emperor Qian Long was a prince, a monk of the most prophetic kind was guided into the palace. As the monk passed by, a white flower from the tree dropped onto the head of he prince Qian Long. The monk exclaimed, "The white is on the king. He is to be the emperor." (The Chinese character for Emperor, "huang" is made up of two parts. The top is white, the bottom is king.) Has not the power of element white given a sovereign sign to Emperor Qian Long?
Thirdly, jade has many colours - black, blue, green, yellow, red, brown, white. According to Chinese culture, yellow belongs to the royalty and red is auspicious. Emperor Qian Long favours none but white. Almost all the jade he owns were white. Be it the big piece of jade he called it the seed of mountains (山子) or the ornaments he carried along to founder with.
He did not say, of course that the white jade is lucky for him (historical events did the saying). He just said that the mutton fat white jade is of the most superior value. The term he used was "shang pin" (上品).
"Pin" does not mean the quality of the matter (which would be called zhi 质). It is also not the value in terms of market price (市价). For he alone was the market as he has already monopolised the whole market by not allowing any layman to own and trade jade.
"Pin" simply means taste. Most superior taste. To read it simply, it just means he finds it most favorable according to his own subjective view.
So is there no objective reason for the liking? He cannot explain. With all wits and intelligence he possessed, I believe he just refused to explain. And it must be to do with bringing him luck.
-- Master Yun Long Zi, 20 November 2013
-- Master Yun Long Zi, 20 November 2013