EDL - This is a bit of a 'nuts and bolts' explanation on the differences in the stone you use and the stone reccommended to you. I did a job in New York state about 10 years ago, and being unfamiliar with the territory (I grew up in Michigan, operate a hardscape/softscape business in Wisconsin), I used what was reccommended to me, which was stone dust. If you hold stone dust in your hand and look at it, it isn't very angular. It's more like big black grains of sand. In Metro Detroit (Michigan) (at least this was true about seven years ago) foundry or 'slag' sand was the overwhelming choice. It's more angular, holds together well, but it's clearly not a good choice now, or at best a risky one. Foundry sands have levels of Cadmium and Lead in them. These two elements cause all kinds of biological problems, but only when their levels are too high. So how can you be sure? You have to contact the foundry the slag comes from every few months and get their test results to be sure the slag is safe. Way too much hassle, especially for something that could harm the children of your customers. In Wisconsin we have huge quantities of limestone. That's what my company uses. This stone is very angular. The reason you want angularity is because the individual stones lock together better and resist movement better than non-angular stones do (ever walk on a beach? The grains are very round, or non-angular. The sand squishes right out under your feet, doesn't it? Same thing with stone dust, over time. And don't get me started on the use of sand over that stone base). Check your local quarries for what they supply for road base. It'll be called something like crusher run, or 3/4- (pronounced three-quarter minus). Depending on what part of the country you live in (I'm guessing East Coast), the base thickness will vary - if you live in Texas, an inch will likely do, for pedestrian traffic. In my neck of the woods, AASHTO specs 4" of stone, but I use 6", for two reasons: 1) better prepared base, and 2) customers will be impressed. In talking this issue over with a few civil engineers (you could do the same where you live), anything over 4", for PEDESTRIAN traffic, isn't necessary. For work I install, of that 6", about 4-5" is 3/4-, the rest is limestone screenings (from about 1/4 down to dust). If you have more questions (and don't live in Wisconsin, i.e. competition of mine), let me know. I started paving with brick in 1985, and have laid a few square feet.