Sidewalk/Walkway Question

I am in the process of putting in a new front walkway/sidewalk. I dug out the walkway, and filled the base with a good depth of gravel (about 8 inches or more). I then layered a layer of slate dust about two inches on top of the gravel. If you are wondering where I got slate dust, it came from a well I had dug and the well went through hundreds of feet of slate, so this dust needed to be used somewhere. So far, everything is working out well.
Anyway, I have flagstones for the surface of the walkway. I need to know what the best material is to use to lay the flagstones in, and to surround the flagstones on the surface? Is regular sand ok? I want something that will not track in to the house much if at all, so it needs to compact down well.
Thanks in advance for any advice.
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