Hi Steve. Toma sent me the following, any comments?
Wells, John H., 1989, Placer examination--principles and practice: U.S.
Bureau of Land Management Technical Bulletin 4, 209 p.
This manual was originally published in 1969; the current version is a
reprint with some changes. It may be a bit hard to find, but any library
that is a depository for Federal Government publications (most major
universities are depositories) should have it.
I have not heard of anyone using cyanide leach for full-scale production
from a placer deposit containing fine gold. The usual application, of
course, is for lode gold ores, which are much higher grade than placers;
there are both vat-leach and heap-leach versions of the method. It could
certainly be applied to placer gold recovery, but to be economic at
typical placer grades, leaching would have to be restricted to
concentrates produced by size classification and probably gravity
separation. Under these conditions, the amount of cyanide-treated
tailings would be a small proportion of the bulk material processed.
Cyanide-bearing tailings must now be disposed of in properly engineered
and managed impoundments designed to promote natural degradation of the
cyanide, and to facilitate dewatering and eventual reclamation."
U.S. Geological Survey |
