Substrate/chemistry issues

[IDMiamiBob@aol.com]

After searching long and hard for some kind of black, or even dark brown 
sand, I settled for some epoxy-coated black lizard sand.  It looks nice, but 
it is obviously not natural.  So I tried finding Tex-Blast from a 
sandblasting supplier.  No one knew what it was, and silica-based media are 
out of vogue because of health risks, but one place offered to provide me 
with silicon carbide.  The lady said it is black, but had no idea as to 
whether it was chemically inert in water.  My intitial suspicions about it is 
that it is some kind of salt and, provided it is relatively insoluble, should 
work fine.  Any knowledgeable folks out there.

My second thoght is that recreational gold "prospectors" separate the gold 
from a substance called "black sand".  Seeing as gold is generally veined in 
quartz, it seems that this black sand is likely to be volcanic, and should 
also be inert.  Some of these guys bring it home by the bucketful and 
separate the gold on a "riffle tube", or even better, they use an acid to 
dissolve the gold, and then reclaim the gold from the slurry.  If I can find 
someone to provide me with their black sand when they are done, is it likely 
to be free of metallic contaminates?

Bob Dixon


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