Doccat5 "GanniGrit" is nothing more than sifted crushed granite. I buy "Granite dust" from a local stone mill (and pay $ 5.00 a ton for it). I mention a finished granite product for people who don't have a local (cheeper) source for ir.
GranniGrit is a chiken feed amendment.
Like I said I buy mine by the ton and sift out what I want for the inert part of the very fast draining soil I use with trees.
The dust (portion of siftings) I use for traction grit instead of salt in walkways and driveways.
As my eldest said most eloquently, "bonsai soil looks like a bag of rocks with a bit of bark mulch drug through it".