Regarding dust, I have to say I saw bad results from substrate mixes where I used perlite which came with massive amounts of dust perlite particles, the sempervivum in those seem to have very slow growing roots, underdeveloped roots.
Sometimes these bags can have 20% perlite dust which is literally making the entire substrate white when mixed. I assumed somehow because of the larger perlite pieces the dust would drain itself out after a while from the containers, but it seems not and maybe it has to do with the fact that perlite floats no matter what and perlite dust does the same.
I would be careful to not have any large amount of perlite dust I guess.
