It's what we call 1/4" minus gravel. It is basically a very fine gravel with lots of stone dust in it. And the risers are reclaimed basalt from the blasting that was needed to create this lot- so yours' should look just as nice :-)

I have to get myself to the stone supplier to see what we have here in lower NY state. Would you please tell me how deep you go down, what larger gravel layer below, if any, and how deep the finish gravel is? Basically, what's your construction specification. How high does the stone riser have to stand proud of the gravel to keep it more or less in place? BTW, THANKS!!!!

We usually do 3"-4" of a larger gravel underneath- but it could easily be done with just the finer gravel. We then do 2"-3" of the 1/4" minus gravel over the top. It compacts very hard, so the riser top and gravel can basically be level to each other.