>The active ingredient in Calgon is sodium hexametaphosphate.

Ah! That is a disaggregant which I overlooked... I have it at work,
but haven't used it.

Another is "hypo", sodium thiosulfate. This can very successfully
release micros from matrix, but will destroy larger specimens. melt
it and pour it over the matrix (or immerse tha lumps in the melt),
allow to solidify, remelt... or something, I'm not exactly sure of
the procedure... you can guess that I haven't used this one either.

My microfossil work has been limited to my own specimens, which have
all responded either to H202 or was in hard matrix, requiring
airscribe work.
--
Regards
Andrew