Substrate - greensand?

Hello all,
        All this talk about substrate lately got me thinking.  I am also
terrestrial gardener, and I use organic approaches.  I mix my own fertilizer
concoctions, and one of the ingredients is Greensand.  It is the source of
Potash/potassium.  My organic gardening reference book says it's 7% total
potash and has 32 trace minerals.  Hummmmm.   It passed the vinegar test but
did leach a little green color.  I then took a little more and added it to
water about 10 times it's volume and mixed it up.  The water has the look of
green tea, a cloudy appearance, nut not muddy and the larger stuff settles
to the bottom.  After 15 minutes the color further lightens to a very weak
tea, maybe if it were rinsed a little most of the color would be washed
away.  But the sand was still a very dark green, so the green color is
through the sand not just a coating.  And as the name implies it's sand.
Has anyone tried this or heard of any benefits/side effects from its use.
It "sounds" like it would be a nice addition to the laterite/gravel mix.  I
am a little concerned that the potash may only be contained in the green
that came off during the vinegar test.  But it is a naturally mined material
and is remove from the ground as "green sand".