I had seen this in photos before and always want to see a closer shot of it.
I always suspected something in the core of these stones but not the whole stone itself with merely a covering.
Weren't these verified as high cobalt content blue stone coming from a particular place far away? Maybe they were chiseled out and had the metal(looks like iron) cast inside? The cobalt quality of the blue stone further enhancing the frequency of the fields?
I have heard stories of people being "shocked" before... now they make alot more sense.