Lead, 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.

Some 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.

These 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.

Optimizations 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.

The 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.

(a) Deposits within close Proximity of the existing operating mines.

Any 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.

Deposits 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.

(c) Deposits mineable by open case.

Deposits 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.

The 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.