Siemens

Two test work programs were completed on samples blended from oxidized sandstone-breccia ore and oxide-intrusive material from the La Arena deposit. Laboratories used for the programs were:

2013 CERTIMIN SA (Certimin), La Arena Site for column test work and bottle roll tests, and

2014 SGS del Peru SAC (SGS)/Certimin, Lima for QA/QC column test work.

Test work at Certimin’s test facilities at the La Arena site was supervised by La Arena staff and concentrated on bottle roll, column leach gold recovery and reagent usage for different samples and blends of bulk material from the Ethel and Calaorco Pits. The column leach test reporting also noted breakthrough times (indicative of initial percolation rate). The test program consisted of 21 bottle roll leach tests and 22 column leach tests.

Subsequent test work in late 2013 and early 2014 at SGS in Lima and Certimin’s test facilities at the La Arena site focused on consistency and repeatability of column tests results for quality assurance (QA). The QA test program consisted of four samples split from the same composite blended sample, two tested by SGS in Lima and two tested by Certimin on site.

13.5.1 2013 Program

The 2013 program test work was conducted in a number of phases. These consisted of bottle roll and column leach tests designed to determine gold extraction and reagent usage with different ore types.

Bottle roll samples were crushed to 100% passing 0.15 mm and leached in a rolled bottle for 48 hours at pH 10 and cyanide strength ranging from 100 to 800 mg/L. As displayed in Figure 13.5-1, gold extraction was in the range of 76% to 91%, sodium cyanide consumption ranged from 0.06 kg/t to 4.09 kg/t, average 0.78 kg/t and lime consumption ranged from 0.6 kg/t to 2.43 kg/t. Those atypical values of sodium cyanide consumption of 2.08 kg/t and 4.09 kg/t correlated with high cyanide strength of 400 and 800 mg/L respectively. The rest of tests were performed with less than 200 mg/L of cyanide and cyanide consumption ranged from 0.06 kg/t to 1.23 kg/t.

Figure 13.5-1 Bottle Roll Tests Results

Twelve column leach tests were successfully leached in open circuit, without barren solution recirculation. The following comments are based on the results presented in Figure 13.5-1:

• The colluvium composite gave gold extraction of 91.5% and reagent consumptions of 0.14 kg/t of sodium cyanide and 0.9 kg/t of lime.

• The oxide intrusive composites 1 and 2 resulted in low percolation performance and gold extraction of 89.0% at 400 mg/L cyanide and reagent consumptions of 0.92 kg/t of sodium cyanide and 2.7 kg/t of lime in the successfully leached column.

• The oxide intrusive from Ethel pit resulted in poor percolation performance and column leach irrigation was halted on the fourth day.

• Five leach column tests were performed with blend composites at different proportions of oxide intrusive and sandstone. The columns used were 2 m high by 0.2 m diameter and the ore samples were crushed to 100% passing 25 mm. All blend composites were successfully leached and gold extraction ranged from 88.2% to 91.2% at 100 – 150 mg/L cyanide with total sodium cyanide consumption ranging from 0.23 kg/t to 0.35 kg/t and lime consumption from 1.6 kg/t to 2.2 kg/t.

• The blended composite with 51% intrusive from Ethel Pit and 49% sandstone was leached successfully. The column used was 6.09 m high by 0.76 m diameter and the sample was crushed to 100% passing 152 mm and 100 mg/L of cyanide strength.

Gold extraction was 74.1% and sodium cyanide consumption was 0.09 kg/t and lime

• Copper head grade did not affect sodium cyanide consumption or gold extraction in the samples tested, but no sample with more than 800 g/t of copper has been tested.

• Eight column tests with composites of 100% oxide intrusive ore were not leached successfully and were stopped because the column showed percolation problems during irrigation.

Table 13.5-1 Column Tests Results

Composite Head Head Tails Extrac. Lime NaCN CN

Success Au g/t Cu g/t Au g/t Au % kg/t kg/t mg/L

Run of Mine Material, Column 6.09 m high x 1.15 m diameter

Intrusive (Ethel Pit) 0.66 538 - - - - - NO

Material Crushed 100% 152 mm, Column 6.09 m high x 0.76 m diameter

Intrusive (Ethel Pit) 0.66 538 - - - - - NO

51% Intrusive (Ethel Pit)

/49%ST 0.36 289 0.1 74.1 1 0.09 100 YES

Material Crushed 100% passing 76 mm, Column 1.98 m high x 0.20 m diameter

Intrusive (Ethel Pit) 0.66 538 - 34.8 1.4 0.05 100 NO

Intrusive (Ethel Pit) 0.66 538 - 28.7 1.4 0.02 100 NO

Intrusive (Ethel Pit) 0.66 538 - 41.4 1.4 0.04 100 NO

Intrusive (Ethel Pit) 0.66 538 - 45.6 1.4 0.05 100 NO

Intrusive (Ethel Pit) 0.66 538 - 49.9 1.5 0.06 100 NO

Material Crushed 100% passing 102 mm, Column 6.09 m high x 0.30 m diameter

Colluvium 0.14 5 0.01 91.5 0.9 0.13 150 YES

Material Crushed 100% passing 38 mm, Column 2.00 m high x 0.15 m diameter

Intrusive Composite 1, 2 0.46 562 0.08 77.6 2.7 0.41 200 NO

Material Crushed 100% passing 25 mm, Column 2.00 m high x 0.20 m diameter 20% Intrusive

13.5.2 2014 Program

The quality control test work was conducted in two column tests at the Certimin Site Laboratory and replication of these tests was conducted at SGS Lima The column leach tests were designed to determine repeatability of gold extraction and reagent usage, with one composite sample split and sent to both laboratories.

The column test samples were crushed to 100% passing 25 mm and leached in a column 2.0 m high by 0.15 m diameter. The sample was 33.3% oxide intrusive rock and 66.7% sandstone.

Column leach tests results are presented in Table 13.5-2 and the following comments summarise the outcomes:

• There were no percolation problems for the columns at SGS or the columns at the Certimin site laboratory.

• It was intended that both 2014 Certimin and SGS tests were undertaken using 150 mg/L cyanide solution. However SGS misunderstood this requirement to be 150 mg/L sodium cyanide, equivalent to 80 mg/L cyanide. However the test results did not demonstrate any material difference in gold extraction.

• Cyanide consumption did not appear to be a function of gold extraction rate, however did appear to be related to the initial strength of the cyanide solution.

• Final gold extraction was similar for the 4 columns tested, in the range of 86.4% to 87.1%.

• Lime consumption was in the range of 1.53 kg/t to 1.56 kg/t.

• Sodium cyanide consumption was low in the range of 0.10 kg/t (80 mg/L cyanide) to 0.16 kg/t (150 mg/L cyanide). Higher cyanide strengths resulted in higher sodium cyanide consumption.

• The kinetic curves of Figure 13.5-2 and Figure 13.5-3 showed similar behavior for the extraction of both gold and copper.

• The percolation of the column test at site was slower than the column tests at SGS, taking approximately 2 days longer to break through (Figures 13-3 and 13-4).

Table 13.5-2 Certimin and SGS Column Tests Results

Composite Head Head CN^- Tails Extrac. Lime NaCN

Au g/t Cu g/t mg/L Au g/t Au % kg/t kg/t

Site Column C-18 0.44 339 150 0.06 86.2 1.56 0.15

Site Column C-19 0.44 339 150 0.05 87.1 1.57 0.17

SGS Column 01 0.49 349 80 0.07 86.5 1.53 0.10

SGS Column 02 0.49 349 80 0.07 86.4 1.53 0.10

Figure 13.5-2 Gold Extraction Curve Kinetics for Column Tests

Figure 13.5-3 Copper Extraction Curve Kinetics for Column Tests