Pulacayo Project Feasibility Study - Apogee Silver

Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report
090644-3-0000-20-IFI-100
13.1.3 Bulk Density
Two rock samples were selected from drill core samples for in-place bulk densities. Each
sample was weighed, waxed and re-weighed, then immersed in water to determine volume of
the sample. The in-place bulk density of the sample ranged from 2.2 t/m 3 (-73.5 #) to 3.4 t/m 3
(-85 #).
13.1.4 Leach Tests
Silver Minerals in the ore were not amenable to leaching, even at the fine grind size. The
silver extraction was extremely poor at the fine grind size of 150 µm, less than 20%,
indicating that silver was not present in the ore in the native form. The NaCN and lime
consumptions were high in the leach tests.
A representative sample of the solid was submitted for determination of silver content by fire
assay technique.
13.1.5 Gravity Concentration Tests
A gravity test was performed to determine the potential of recovering silver and other sulfide
minerals by gravity concentration. A 2 kg sample was stage ground to P100 of 48 # (0.297
mm) and processed over a Deister table. The Deister concentrate was re-processed on a
Gemini table.
The results indicated that the sample was not amenable to gravity concentration for silver
recovery since the recovery of silver minerals was only 17% in the Gemini concentrate.
13.1.6 Flotation Tests
13.1.6.1 Grindability
A grind study was initiated to determine the laboratory grind time vs. particle size relationship.
The grind time requirement to achieve a P80 of 150 # (104 µm) was determined from the
grind data, this being 20 minutes for the composite sample.
13.1.6.2 Bench Scale Open Circuit Flotation Tests
Bench scale open circuit flotation tests using the composite samples was performed using
the flotation reagent suite developed for the San Cristobal Project. The flotation process
consisted of grinding the ore with lime (pH > 8) and ZnCN followed by conditioning the
ground pulp with more ZnCN, AP­238 collector, sodium isopropyl xanthate (SIPX) and
frother, methyl isobutyl carbinol (MIBC). The lead minerals were floated and the rougher
concentrate was cleaned once. The lead rougher tails were conditioned with lime and copper
sulfate and zinc rougher concentrate was collected using SIPX and MIBC. The zinc rougher
concentrate was again cleaned once.
The overall silver recovery in the lead and rougher concentrates was 97.1%.
The lead cleaner concentrate recovered 2.8% of the weight, 84.6% of lead, 3.1% of zinc and
46.9% of silver. The lead concentrate assayed 60.8% Pb, 4.22% Zn and 8,440 g/t Ag.
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