That was the first time I heard about this stuff. I turned to my good friend KM Chee, whom I can always count on for advice for such matters, to enlighten me.
"舍利子”is called "Sharira" in Buddhism or in the Sanskrit language. Apparently, they are crystals that remain behind after a body has been cremated. Most monks and even those who are strictly on a vegetarian diet and pursuing spiritual development would also leave behind crystals when their bodies are cremated. The collection of 舍利子 that my contact was referring to is said to be from the cremation of Sakyamuni Buddha after his passing to Nirvana!
Out of curiosity, I wrote to another friend in China. She said these relics could not be sold or bought; they had to be “song” (送) or gifted. I also surfed the net for more of it. I was surprised that there were so many websites talking about it.
I always thought simplicity is the hallmark of this religion. How wrong I have been! I sure have learned a great deal from all these.