Roger,
Garnet sand is a very common sandblasting media. Call any sandblastin supplier in your area and they probably have it. Mine is 16 mesh if I'm not mistaken, I couldn't find coarser one. 100 lbs. bag is about $37.
I tried to find quartz but that seems impossible, especially in dark colors. Dennerle has 6 different colors of pure quartz but as we all know they don't sell many items in the US, especially gravel.
One may be interested in using glass beads, which are another common sandblasting media. But Edward told me that the light that penetrates the beads leads to algae growth in the substrate. How's that for weird

So seems that glass beads are ruled out, unless one can find cheap colored ones. Some craft websites have all kinds of colors but they sell the beads by the ounce...
Planting the tank:
My first intent was to do what Carlos suggested - make the scape appear higher by using tall "skinny" leafed plants. Then I thought the opposite - jsut like you suggest - what about keeping it low? But the height of that tank almost requires a tall plant arrangement. I have not decided yet, plus I don't have all the plants I wish I had

. Carlos is right about the Eleocharis vivipara, I hadn't taught about it, I wish I had it!
In any case this time I want to keep more of the rock/wood exposed. Glosso will be the ground cover for sure, but not as a "cover all" mat. The garnet does seem very beautiful upon close examination, but from 2 feet away it doesn't look that clear and exotic. At least it doesn't look like purple crystals, something I was concerned about.
The previous layout in this tank, which you can see
here , taught me what Carlos mentions - the original layout may be great (or not that great) but the plants can make the difference. I personally don't see a point of having a precise, elaborate rock/wood arrangement only to have it burried and hidden later with lush plant growth. I still can't understand why Amano has done exactly that in more than a few occasions.
Carlos,
I did some sloping but not as aggresive as yours - I'd say 2 inches on the back, 1/2 inch on the front. You can somewhat see the thickness in the back
here but unfortunatelly I've blacked out the line of the bottom glass.
How tall does E. vivipara get?
--Nikolay