Earlier quoted context omitted.
It's generally considered safe. It's sold as an additive to livestock feed, though I don't know what the purpose there is. It's very finely ground volcanic rock. The particulates have very sharp edges which shred insect exoskeletons. It doesn't hurt your skin though. It might cause a problem if inhaled, similar to silicosis but that's mostly a guess. Some people leave a line of it on windowsills or door thresholds to…
> It's very finely ground volcanic rock. Wikipedia is pretty clear that it's finely ground fossils. (It also says that it's sedimentary rock, as is necessary for fossils. Fossils can't be volcanic rock; their structure would be destroyed by melting.)
Breathing it for long periods of time wouldn’t be ideal.