About 14 years ago "carnelian" was scarce.
I was told it was because what we had thought was carnelian,
the beads of one color, was really Brazillian onyx that was dyed to be that color.
Maybe under an electron microscope it's all the same.
European countries had cracked down on the dye used and
it took a while to come up with a new and acceptable dye.
I think the "goldfish" carnelian, the multicolored ones, are natural.