[dice]

For the granite dust, if I remember correctly they were
mixing it into seedling mix or amending fields where they
were starting tree seedlings with it, then noticing how much
better the trees grew over several years. I don't know if
top-dressing it on the soil below mature trees will have
comparable benefits, especially in an arid region where there
is not much rainfall to wash it down into the soil.

If you come across some for free, though, it cannot hurt to
scatter it around under them. Places that make monuments,
headstones, granite countertops, etc usually have piles of
it around that they will gladly let people cart off.

I was amazed myself to see all of the mycorrhizae links.
I presumed that if the search turned up a couple of documents
where some researcher had studied the interaction of
mycorrhizae with some species native to the area or grown
commercially there, that would be unexpectedly lucky.
Apparently there are some researchers at UWA for whom
this is their specific field of focus.