Jocelyn, there is a problem with using beach or river sand in
tumblers for rocks. Remember that sand is just rocks in miniature.
Rocks that have been repeatedly swirled in water, such as comes on
beaches and rivers, tends to have very rounded outer shapes. These
rounded forms don’t work as effectively as sharper forms. I’ve heard
of people using “sharp” graded plasterers sand which can be
purchased in varying quantities, but they only used it for the most
preliminary polishings. The commercial grit is graded as to particle
size and is used to obtained finer and finer degrees of polish. As
always there are caveats, that is to say that,you may give your sand
a try and check out the results. I could be wrong. Generally though
I believe that using beach sand will take a much longer time and
produce an inferior polish. It will likely only get the rocks
slightly polished.
Mike