Here in Indiana I have sampled puddingstones which is a "damn hard"
metaconglomerate. The biggest problem I have had is that the conglomerate
is very quartz poor, so I have had to process huge samples to get the 200g
of quartz (pre-50% etch) I require to get a good 10Be/9Be ratio. If you
are working with 36Cl this probably will not be a problem. Which are you
working with? Also what is the approximate age of the deposits? If they
are very old you must be aware of the shorter half-life of 36Cl.