In FML article 1228 Bob Martin <[log in to unmask]> says
 
> 3.  Litter:
>     Clay caution and hint. Berrylium Oxide or silica is often listed
>     as a content of clay, even minute particles are dangerous to you
>     and me, and probably to ferrets too. Avoid it.
 
I don't know about the healthfulness of beryllium oxide but silica is silicon
dioxide, not beryllium oxide.  Silicon dioxide, also known as quartz, is the
main ingredient of sand.  I've sometimes seen silica as an ingredient in
powdered foods where I think it is used to make the mix flow better.
 
--- Bill Sebok
[Posted in FML issue 1229]