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Rio Alto Mining Ltd
Symbol RIO
Shares Issued 168,557,582
Close 2011-06-15 C$ 2.18
Market Cap C$ 367,455,529
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Rio Alto Mining drills 134 m of 2.29 g/t Au at La Arena

2011-06-15 14:39 ET - News Release

Mr. Alex Black reports

RIO ALTO DRILLS 134 METRES OF 2.29 GRAMS OF GOLD PER TONNE

Rio Alto Mining Ltd. has released assay results from 18 reverse circulation drill holes within and around the Calaorco pit at the La Arena gold oxide mine located in Peru.

                         SIGNIFICANT INTERCEPTS 

Hole                                      Intercept (m)    Gold grade (g/t)

CA-R11-018                                         184                0.84
CA-R11-020                                         134                2.29
CA-R11-021                                         274                0.51
CA-R11-022                                         200                1.43
CA-R11-024                                         296                0.69
CA-R11-025                                         210                0.62

Rio Alto previously announced an 11,700-metre RC drilling program at the Calaorco pit. Based on the results obtained from the first 32 holes, totalling 9,029 m, management has decided to increase the program by 3,000 m to 14,700 m in approximately 55 holes. Rio Alto will deliver an updated resource model for the Calaorco pit during the fourth quarte of 2011. Management expects that this drilling program will:

  • Result in positive changes to the resource block classification;
  • Define new resource blocks;
  • Identify new areas to test in order to increase resources.

On April 26, 2011, the company reported the results from 14 holes totalling 3,755 m. This announcement reports the results of an additional 9,029 m in 18 holes. All holes, except one, intercepted gold mineralization in excess of the current mining cut-off grade within and outside of the current pit design.

The results of the most recent 18 holes within the oxide breccia sandstone are outlined in the associated table.

Drill results

References to pit location in the associated table refer to intercepts within the Calaorco oxide pit or drill hole intercepts that extended below the Calaorco oxide pit. A map illustrating drill hole locations and selected drill hole cross-sections related to this press release may be accessed on the Internet.

                         CALAORCO PIT DRILL RESULTS

Hole ID              From    To  Interval (m) Au (g/t) Ag (g/t)  Pit location

RC15                   88   104           16     0.41     0.40   Inside
RC16                  182   200           18     0.33     0.92   Inside
RC17                    0    40           40     3.44     0.28   Inside
including              18    34           16     6.08     0.33   Inside
RC17                  112   166           54     0.36     0.21   Inside
RC17                  236   300           64     0.38     0.33   Inside
RC18                    0   184          184     0.84     0.30   Below
including              18    54           36     2.17     0.29   Inside
RC19                  122   150           28     0.25     0.52   Inside
RC20                    4   138          134     2.29     0.59   Inside
including              48    60           12     6.00     0.42   Inside
including             104   114           10     6.12     0.62   Inside
RC21                    0   274          274     0.51     0.51   Below
including              56    70           14     2.52     0.96   Inside
RC22                    0    20           20     0.28     0.21   Inside
RC22                   88   288          200     1.43     0.26   Below
including             132   186           54     3.55     0.32   Inside
including             174   182            8    16.02     0.20   Inside
RC23                    4    32           28     0.56     0.21   Inside
RC23                   54    78           24     0.60     0.79   Inside
RC23                  100   162           62     0.29     0.30   Inside
RC23                  178   196           18     0.58     0.56   Inside
RC23                  218   252           34     0.28     0.42   Below
RC24                    2   298          296     0.69     0.41   Below
RC25                    0   210          210     0.62     0.26   Below
including              80    94           14     3.05     0.26   Inside
RC25                  242   260           18     0.45     0.20   Below
RC26                   72   106           34     0.72     0.62   Inside
including              74    76            2     8.13     2.40   Inside
RC26                  246   300           54     0.32     0.41   Inside
RC27                  214   336          122     0.37     0.37   Below
RC28                   18   264          246     0.33     0.42   Below
including              22    26            4     1.61     1.35   Inside
including             102   108            6     1.47     0.33   Inside
including             220   226            6     1.06     0.67   Below
RC29                   10    28           18     0.45     0.20   Inside
RC29                  104   146           42     0.19     0.58   Inside
RC30                    0    34           34     0.11     0.20   Inside
RC30                   86   106           20     0.13     0.34   Inside
RC30                  164   178           14     0.22     0.23   Inside
RC30                  264   306           42     0.20     0.31   Below
RC31                  Below the cut-off grade
RC32                   32    54           22     0.22     1.18   Inside

There are two RC drill rigs working at La Arena. By the end of June, four diamond drill rigs are scheduled to arrive on-site.

Approximately 500 m north of Calaorco, a new exploration target, Astrid, has been identified by surface mapping and geochemical sampling. This target has the same geological and geochemical characteristics as Calaorco. At Astrid, the company plans to run 20 kilometres of IP and ground magnetic lines to identify drill targets.

Quality control and assurance

Sampling of the reverse circulation drilling and sample preparation were performed by Rio Alto personnel and were carried out under strict protocols recommended in the NI 43-101 technical report dated July 31, 2010, prepared by Coffey Mining Pty. Ltd. for the company. Samples were taken every two m and split in half to yield seven-kilogram-to-10-kilogram samples. Drill sample recovery was generally in excess of 90 per cent. Rio Alto has a rigorous QA/QC program to control the chain of custody of samples, and the insertion of blanks, duplicates and certified reference standards in each batch of samples. Samples were shipped to CIMM-Peru in Lima where they were dried, crushed, pulverized and assayed. All gold assays were obtained by standard 50-gram fire assaying with AA finish. All silver assays reported in the press release were obtained by aqua regia dissolution followed by ICP measurement. CIMM-Peru is an ISO 9001:2000-certified laboratory.

Enrique Garay, MSc, PGeo (AIG member), vice-president of geology of Rio Alto, is the qualified person responsible for the management of the exploration program and disclosure of the drill results as defined by National Instrument 43-101. Ian Dreyer, BAppSc (AUSIMM member), of Coffey Mining, a qualified person as defined by National Instrument 43-101, designed and reviewed the quality control and assurance program carried out by the company with respect to these drill results. Each of Mr. Garay and Mr. Dreyer has read and approved the scientific and technical information in this news release.

We seek Safe Harbor.

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