zinc, and copper ores occur as unimetal, bimetal and multimetal
type deposits, such as copper deposits, lead deposits
and zinc deposits. They also occur as bimetal such as
zinc-lead deposits and as multimetal type consisting of
lead, zinc and copper ores.
of the unimetal deposit types are Agnigundala (Andhra
Pradesh) Sargipalli (Orissa) lead deposits, Zawar group
of deposits Rampura - Agucha (Rajasthan), Gorubathan (West
Bengal) as lead zinc deposits. The multimetal type deposits
are at Rajpura Dariba, Deri (Rajasthan), Ambamata (Gujarat),
Askot (Uttar Pradesh), Rangpo (Sikkim), etc.
three types of deposits occur with a variety of host rocks
and economic extraction of these deposits depend on the
grade compaction and recoveries at the ore benefaction
plants design to produce concentrates, Most unimetal type
deposits with the host rocks of dolomite, calcsilicate,
and schists are amenable to benefaction and can produce
acceptable grade and recoveries at the benefaction plants.
Even in case of bimetal deposits with host rocks of dolomite,
calc-silicate, quartzite and schist are also technically
amenable to benefaction and the conventional flow sheet
can produce acceptable grade and the recovery of concentrates.
Multimetal deposits, however, in most cases pose problem
in producing clean concentrates of acceptable grades and
recoveries. This in generally due to grain size distribution,
interlocking characteristics resulting in loss of metal
in tail losses. Consequently, multimetal type deposits
are not easily amenable to benefaction.
of grade and concentrate recoveries generally depend on
mineralogy of the ore types and also on the gangue association.
Sulfide ore deposits with graphite, mica and talc generally
are not easily amenable to benefaction and act as hostile
host rock which does not allow to produce acceptable grades
and recoveries of the concentrates. These are the most
difficult types of deposits to be economically exploitable.
cut-off limits to broadly indicates the economic viability
of exploration projects will depend on one or the other
conditions stipulated above. However, with the present
day pricing and input cost of production the following
generalized guidelines may be used.
Deposits within close Proximity of the existing operating
now deposit within close proximity of the operating mine
where the infrastructure exists can be economically exploited
by underground open slope mining with a global grade between
6-8% Pb + Zn metal, subject to accepts able grade and
recoveries of the load-zinc concentrates.
(b) Deposits located in remote areas.
located in remote areas requiring now infrastructure would
however, need an average grade of + 10% Pb + Zn, subject
to achieving acceptable grade and recoveries of the concentrate.
Deposits mineable by open case.
likely to be mined through open cast mining with favorable
ratio of ore to burden and acceptable grade and recovery
can be exploited up to 5 to 7% Pb + Zn.
above figures depend on the present day input cost and
the realization value of the product and would require
modification from time to time and accordingly may only
be used as broad guides.