Well... I received my answer on Pavestone Sand from Pavestone themselves. The following is the reply to an email I sent them today:
Scott,
Thank you for your interest in Pavestone products. To answer your question, our High Desert Sand is silica based, not aragonite. Great timing on your question, by the way. I was asked this exact question a week ago and I had to research the answer. That research has already proved its worth. Thanks again for your question.
Steve Hain
Pavestone Co.
Hagerstown, MD