I've got 500 LBS of the stuff in my garage. The picture on the link posted is not what the 50LB bags I have look like. Sorry but I don't have a jpg of it right now. If I remember right the bags of Southdown from Home Depot are red and blue. They also have "Not for aquarium use" printed on the bag.
Its worth a try. Years ago it was bought up and the name was changed to Oldcastle/Yardright or something like that. I see that bag now says Colorscape on the side but it still says its a "soft texture" "extra fine" and not for traction so that leads me to believe its aragonite or calcium based and not silica sand.
I would buy a bag if they are close by and give it the vinegar test. It would be nice to find again, I used up my 500 lbs a long time ago myself.