As has been pointed out, gangue in any instance is all those minerals in an
ore body which do not form part of the final, saleable, concentrate.
Thus on the Marampa iron ore mine I worked at in Sierra Leone, an open-cast
mine where we were stripping layers off the top of a hill (so not really an "open pit")
the ore was hematite in a micaceous schist. This was treated in a gravity separation
plant which had over 900 Humphreys spirals. The ore entering the mill contained
grains of hematite, mica and quartz and the objective in the plant was to
separate the former from the latter two. Thus, despite Keith Nichols' objections
to the term in this context (why is that, I wonder?), the mica and quartz were in
that case the gangue minerals, discarded to tailings dumps as waste.
Some years later, when working for a consultant and doing a feasibility study
for the establishment of a glass-making industry in Nigaragua, one of the
proposed raw materials was quartz. Sadly, the deposit where it was proposed to
quarry this also contained some limonite, etc, so in that instance the iron-bearing
minerals would have been the gangue and the quartz the valuable one.
Having said that, I would like to echo Richard's comment: What I can't understand
is why you are doing this? It would be interesting to know what the object of the
exercise is.
Tony Brewis
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