it's very doubtful it's aragonite. it's most likley silica. either way it will be ok for your tank. but you want to make sure that it is cleaned and doen't have concrete or other particles in it (it doesn't have to be sterilized)((but that is better)). usually the only time you find aragonite is in tropical play sand like southdown, new castle, etc. (good luck finding that
). if you have any doubts call the company.