Hmmmmm, just tried to post this and I got kicked out...round two..
So I stopped to check the mail, which is at the County Road/Hwy intersection, and there is a long part of the CR that allows for vehicle stops between the highway and our private road, so sometimes things get dropped off there. Anyway, I noticed a pile of maybe 300 lbs or so of this fine gray sand. I got excited, thinking what a nice picotope substrate it would make, so I stopped to get some. When I got up to it I noticed it was actually fine, uniform round beads of various shades of gray. I scooped up about 10 lbs of it.
I have no clue what this stuff is, and I am hoping that someone here will know or have some ideas.
In the meantime, I am going to test it out in a glass on my desk using some Crypt x willissi 'lucens' and a chunk of Anubias 'nana petite' that I was going to have to toss out anyway.
Here are the pics: