Bruce,It is very unlikely that any product sold in the US would have
asbestos in it without huge warning labels all over it. The fibers
do not look like asbestos either they look like alumina silica fiber
which is put in investment requiring higher strength. I could also be
fiber glass as that is sometimes used.
If you are concerned about your lungs do you use proper source capture
ventilation and or a respirator when handling investment? Breathing
sub ten micron sized silica dust can ruin your lungs and cause
silicosis it is very similar to black lung. It requires long term
exposure but if you smoke it increases your chances of problems from
the silica tenfold.
James Binnion Metal Arts
4701 San Leandro St #18
Oakland, CA 94601