Hi   I've just had 5 tonnes or so of drainage stone delivered (limestone). It is supposed to be clean / washed.   It doesn't look too clean to me, but then I've never bought it before and so have nothing to compare it to. I asked the driver and he said it is definitely clean and not to worry - that's just how it comes from the quarry.   So it's over to you guys.... Here's my hand after holding a handful some for a few seconds, followed by some photos of the stone: