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TORONTO, ONTARIO–(Marketwire – Oct. 17, 2011) – Atacama Pacific Gold Corporation (TSX VENTURE:ATM) (“Atacama Pacific”) is very pleased to report further positive results from metallurgical testing from the it’s oxide-associated Cerro Maricunga Gold Project located in northern Chile, 20 kilometres south of Kinross Gold’s La Coipa precious metals mine. The testing was undertaken by Laboratorio Plenge (“Plenge”), Lima, Peru and by Advanced Mineral Technology Laboratory Ltd. (“AMTEL”), London, Canada.
Gold recoveries ranging from 76% to 83% (Table 1) were achieved from three column percolation leach tests undertaken by Plenge at a crush size of 100% passing 1 inch (25 mm) over a period of only 20 days. Gold recoveries were fast with the majority of recovered gold extracted during the first 10 days of the column tests. Cyanide (NaCN) consumption was lower than in previous column test work varying from 0.7 to 0.9 kg/t. The columns were not optimized for NaCN consumption. Projected NaCN consumption in production heaps is typically 25 to 33% of that consumed during laboratory testing.
In addition to the column test work, Plenge obtained gold recoveries of 72% to 90% from a series of nine 48 hours bottle rolls tests (Table 2) undertaken on material crushed to 100% passing 1.7 millimetres (10 mesh). A subset of each sample prepared by Plenge was sent to AMTEL for confirmatory bottle roll tests (96 hour) returning gold recoveries of 80% to 93% on material crushed to 80% passing 0.8 millimetres. The slightly higher recoveries achieved by AMTEL are largely the result of the tests being completed over a period of 96 hours as compared to the 48 hour tests completed by Plenge.
| Table 1 – Column Test Results (100% passing 25 mm) | |||||
| Sample | Zone | Gold Grade | Gold Recovery | NaCN | Lime |
| (g/t Au) | (%) | NaCN (kg/t) | Lime (kg/t) | ||
| Comp A | Phoenix | 0.87 | 76 | 0.9 | 3.2 |
| Comp B | Lynx | 1.04 | 83 | 0.7 | 2.3 |
| Comp C | Crux | 0.70 | 82 | 0.8 | 2.9 |
“The expanded metallurgical program continues to demonstrate that the gold mineralization at Cerro Maricunga is amenable to heap leach processing”, said Carl Hansen, President and CEO of Atacama Pacific. “The strong gold recoveries achieved across various gold grades combined with the fast recoveries were very encouraging and provide us with a base for the upcoming preliminary economic study. The metallurgical program is ongoing with AMTEL and Kappes, Cassidy and Associates, Reno, Nevada continuing testing. As part of the continued program, in conjunction with our upcoming 42,000-metre, Phase III drill campaign, large diameter diamond drill core samples will be collected across the deposit with the goal of developing a metallurgical model for Cerro Maricunga.”
Oxide-associated gold resources at Cerro Maricunga stand at 92.8 million tonnes grading 0.54 gram per tonne gold (“g/t Au”) for 1.62 million ounces of gold in the indicated resource category at a 0.3 g/t Au cut-off and a further 116.7 million tonnes grading 0.52 g/t Au giving 1.95 million ounces in the inferred category (see August 24, 2011 press release).
Metallurgical Test Details
The metallurgical test charges were prepared from quartered diamond drill samples. As noted in Table 3, three samples were collected from each of the three gold zones (Phoenix, Lynx and Crux zones) comprising the Cerro Mariucnga gold deposit. The individual samples collected were combined to form a composite column test charge for each zone.
Column percolation tests Comp A, Comp B and Comp C consisted of charges of 35.0, 44.9 and 37.2 kilograms, respectively, stacked in 16 by 160 centimetre columns. An alkaline cyanide solution continuously cycled through the columns at a rate of 10 litres per hour per square metre of column surface area with cyanide strength maintained at 0.1% NaCN. Protective alkalinity was maintained at a pH level of 10 to 11 by the initial addition of hydrated lime during the column setup and with the addition of further lime to maintain the alkalinity.
The column tests continued for a period of only 20 days which included 3 days for final drainage and washing. Leach solutions were tested daily for pH and NaCN, gold and silver content. Gold recoveries, as reported in Table 1, varied from 74.4 to 83.0%. Silver head grades averaged 0.51 g/t and recoveries were minimal varying from 14 to 27%. Compaction of the completed columns was minimal showing a reduction in stack height, compared to the start of the test, of 2 to 3%.
The Plenge bottle roll tests were undertaken on approximately 1 kilogram charges run for a period of 48 hours at 40% solids. Alkalinity was maintained between 10 and 11 and cyanide concentration was kept at 0.1%. The AMTEL bottle rolls tests were performed on 0.8 kg charges at 33.3% solids. The pH was held between 10.5 and 11 with hydrated lime and a cyanide concentration of 0.1% NaCN was maintained.
Atacama Pacific’s metallurgical testing program is managed by AMTEL (Advanced Mineral Technology Laboratory Ltd), London, Canada. Plenge is a Lima, Peru -based metallurgical laboratory specializing in investigative metallurgical testing and plant design and engineering with a focus on South America projects.
| Table 2 – PLENGE Bottle Roll Test Results (48 hour tests; 100% passing 1.7mm – 10 mesh) | |||||
| Sample | Zone | Gold Grade | Recovery | NaCN | Lime |
| (g/t Au) | (%) | (kg/t) | (kg/t) | ||
| Comp 1 | Phoenix | 1.47 | 87 | 0.7 | 2.5 |
| Comp 2 | Phoenix | 0.82 | 81 | 0.7 | 2.7 |
| Comp 3 | Phoenix | 0.39 | 80 | 0.7 | 5.1 |
| Comp 4 | Lynx | 1.78 | 90 | 0.7 | 1.9 |
| Comp 5 | Lynx | 0.76 | 85 | 0.8 | 2.4 |
| Comp 6 | Lynx | 0.36 | 72 | 1.0 | 2.5 |
| Comp 7 | Crux | 1.00 | 88 | 0.8 | 2.7 |
| Comp 8 | Crux | 0.70 | 82 | 1.5 | 3.0 |
| Comp 9 | Crux | 0.42 | 83 | 1.1 | 2.5 |
| Table 3 – AMTEL Bottle Roll Test Results (96 hours; 80% passing 0.8 mm) | |||||||
| Sample | Zone | Gold Grade | Recovery | NaCN | Lime | Sample Location | |
| (g/t Au) | (%) | (kg/t) | (kg/t) | Drill Hole | Meters | ||
| Comp 1 | Phoenix | 1.54 | 92 | 0.2 | 3.2 | CMD-026 | 260-272 |
| 280-292 | |||||||
| Comp 2 | Phoenix | 0.78 | 84 | 0.4 | 4.1 | CMD-037 | 76-94 |
| Comp 3 | Phoenix | 0.37 | 81 | 0.3 | 6.9 | CMD-010 | 30-40 |
| Comp 4 | Lynx | 1.98 | 93 | 0.3 | 2.8 | CMD-049 | 50-56 |
| Comp 5 | Lynx | 0.82 | 88 | 0.4 | 3.8 | CMD-058 | 146-154 |
| CMD-049 | 74-86 | ||||||
| Comp 6 | Lynx | 0.38 | 80 | 0.2 | 3.8 | CMD-058 | 108-118 |
| CMD-038 | 64-72 | ||||||
| Comp 7 | Crux | 1.21 | 91 | 0.3 | 4.2 | CMD-011 | 108-118 |
| CMD-056 | 64-72 | ||||||
| Comp 8 | Crux | 0.67 | 86 | 0.6 | 4.7 | CMD-014 | 230-248 |
| Comp 9 | Crux | 0.34 | 85 | 0.6 | 4.3 | CMD-027 | 48-56 |
| CMD-031 | 58-68 | ||||||
Grant of Options
Atacama Pacific has granted an aggregate of 120,000 options of which 100,000 were granted to a director of the corporation and 20,000 were granted to a consultant. Each option entitles the holder to acquire one Atacama Pacific common share at an exercise price of $4.50 until October 13, 2016.
About Atacama Pacific Gold Corporation
Atacama Pacific’s business is the acquisition, exploration and development of precious metals resource properties in Chile. Atacama Pacific’s principal mineral property is the Cerro Maricunga oxide-associated, breccia-hosted gold project, located in Region III, 140 kilometres by road northeast of the city of Copiapo and its goal is to become a producer of gold through the exploration and development of the Cerro Maricunga Gold Project. Atacama Pacific also has interests in four other mineral properties within close proximity to the Cerro Maricunga Gold Project and a fifth property in Chile’s Region I.
National Instrument 43-101 Compliance
The Cerro Maricunga resource estimate was prepared under Canadian Institute of Mining, Metallurgy and Petroleum (“CIM”) Definition Standards (2005). Michael Easdon is the independent qualified person, as defined by National Instrument 43-101 (“NI 43-101”), for the resource estimate and Mr Easdon review and verified the contents of this press release. SRK Consulting (Chile) S.A undertook to prepare and is responsible for the resource estimate. Joled Nur, Geostatistical Engineer for SRK Consulting (Chile) and a member of the Australasian Institute of Mining and Metallurgy, is the qualified person who prepared the resource estimate.
