Thanks again. My first thought was - no quarries, since hardly anyone lives here. But yes there actually is a quarry! Maybe even two, owned by that guy with the fancy house who simply digs his money out of the ground every year
They crush rock for roadwork and I'm not sure if they produce 'fancier' grades, but they might, and there must be dust produced, regardless.
I've been in lots of areas where I had access to glacier valleys but unfortunately this isn't one of them. This area was glaciated historically but there aren't any active glaciers to be found now- everything is covered in nearly impenetrable rainforest and brush, and to get up into some alpine country where I might find exposed rock would be an epic struggle.
About the only exposed rock is in the tidal zone or in very cliffy areas.
However, in the tidal zone there is a lot of sedimentary rock- the consistency of hardened clay, with plenty of fossils of sea creature shells in it.
Looks like I have some reading to do (well, I already knew that I'm just procrastinating) to understand more about this- and what elements I am trying to get from the rock dust, and whether some rock is better than other rock, etc.
Thanks again for the great replies.
Edit- Oh yeah - creek and river mouths. That is an option- and probably would give me a great mix of mineralized muck if I start digging around.
The thing that slows me down with the organic cannabis gardening recipes is the 'pinch of this, and a peck of that, and a dash of that for good luck' sort of approach. Easy maybe once you get your feet wet, but slightly confusing before that.