Dunno, a friend with jeweler's training and equipment did it. I think she had a diamond drill bit. I've asked her, and in the mean time, I found this....
edkrueger wrote:For someone who know nothing about drilling holes in things, how did you do it?
"With a diamond bit on a drill press. The ceramic needs to be under water while drilling, and a flex shaft is ideal because it can drill at lower speeds. Go slowly in and out to release the ceramic dust and keep things from heating up."