GL,
I could not find the southdown product. I sent them an email and they said there product was not available in my part of the country.
Finally I found a place on the other side of Sacramento CA, that had dolomite sand. When I arrived I found that they had several grades. All grades were the same cost; $3.50/50lbs. I bought 4 bags of the fine sugar sand grade, and 4 bags of a more corse gravel/sand, and two bags of 3/8" grade. In the end I found that the sugar sand was too fine and I put it a side for some other future use. The coarser grade ended up being just right. I created trails of 3/8" grade to give it a little character. Done