Was at a stone and gravel place and saw a pile of what they call crusher dust. Is VERY fine limestone from "dust"/ sand to pea sized. A by product of crushing limestone into sized rocks. Would this work for topping my potted figs (1" or so deep) like I have seen/heard or will the "dust" portion be too readily available and be dissolved all at once and wreak havoc???? They want $30.00 / ton. They also had 1" -2" limestone for driveways etc that had some of this mixed in. Potted fig experts please weigh in. Did a quick search and could find nothing conclusive

The dust is calcium carbonate which is not very soluble or very available.  Just like the limestone rock.  The "lime" that is used to raise pH is calcium hydroxide.  http://en.wikipedia.org/wiki/Lime_(material)

I would wash it to remove the finest particles so as not to get a compacted layer. I have no idea how it will intereact.

Greg,

Most stone yards sell this material as a means to reuse concrete. Be sure not to get the finer material as this will compact over time and not allow water movement. Being concrete the main material used in the base is lime stone and due to this crush and run will cause mixes to swing toward basic on the pH scale. 

So. What I am hearing is that I probably don't want to use this?

Greg, your better off with cheap angular silica sand. 

Thanks guys

You don't want calcium hydroxide, that'll kill your plants.  Limestone is what you want, but not dust.  Dust will smother the roots.  See if you can get coarse sand to small gravel size.