Rock Dust

We are about to get around 10 tons of rock dust for our garden. I just found out about this stuff, and from what I read on the internet it seams like great stuff.
Anyone on here use it before? If so what were the results, and any recommendations.

 

What kind of rock ?

Here, we have ground limestone spread from time to time to "sweeten" an otherwise acid soil.

 

From a rock quarry, or gravel, or even lava. Look up rock dust on-line, you might be surprised.