if it's the stuff I'm thinking about, it's calcite, which is similar to aragonite, but dissolves at a much lower pH (so it will not buffer anything in your tank the way aragonite will, it'll be more inert like silica sand). I had this in my brackish tank a few years back before i converted it to salt water (it was sold under a different name, by Seachem I think)
Depending on grain size it may trap detritus, but chemically it is OK to use. The grains in the one I had were tiny, about the same as oolitic sand.