I'm not an expert. But I think it's "copper oxide" or "cupric oxide". CuO. I think that gets your turquoise and green.
And copper in a more pure form may be used to get reds.
We're straying from the topic in a big way.
Might be cool to start a new thread on the blueboy versus superboy examples.
Or could add them in the marble comparison thread here:
http://marbleconnection.com/topic/20318-marble-comparison-thread/
David Chamberlain received some of the marbles and communicated with the seller and clarified some points. They were acquired in France but had a label/information saying made in Vietnam. Acquired around 2000, so could be from the 1990's.
So, I guess these marbles which we thought of has "handmade in China" may have come from places like Vietnam as well or instead.
Not earth-shattering news. But it got me going for a minute, seeing a different country name there.