Its called Mystic White II - made by U.S. Silica Company. Its a larger diameter then play sand and has a mixture of white and off-white granules. I've been using it for almost a year in my 55 gallon with no sand discoloration or effect on my water perimeters (7.0
pH).
I found the product online and called the company to see where I can buy it - it just happened to be carried at my local Pool Store for $8 a 50lb. bag! I thought I would share with everyone since it worked out so great for me. Here is link to the website:
http://www.u-s-silica.com/mystic.htm
Here is link to pics of my tank if you want to see the sand in action:
Remodeled 55G Tank Pics