Friday, July 05, 2013 10:41:24 AM
Silver Bull Announces Updated Metallurgical Test Results On The Silver Mineralization At The Sierra Mojada Project, Coahuila, Mexico
Vancouver, British Columbia -- July 2, 2013 -- Silver Bull Resources, Inc. (TSX: SVB, NYSE MKT: SVBL) ("Silver Bull") is pleased to provide interim results and a metallurgical flow sheet for its metallurgical test program on the silver mineralization at the Sierra Mojada project located in the state of Coahuila, Northern Mexico.
Results reported in this news release pertain to test work conducted by Kappes, Cassidy and Associates, Reno ("KCA") on the silver mineralization from the three areas of the silver deposit: "Shallow Silver Zone, "Centenario Zone", and "Fonteriza Zone", and on SART test work (a metallurgical process that regenerates and recycles the cyanide used in the leaching process of the silver) performed by BioteQ Environmental Technologies Inc. ("BioteQ"). This news release does not include work on the "High grade" zinc zone which is still ongoing and sits underneath and adjacent to the silver mineralization.
HIGHLIGHTS INCLUDE:
* An overall average silver recovery of 73.2% with peak values ~89.0%
* Recovery of between 40% - 50% of the "low grade" zinc mineralization at the SART stage, previously thought unrecoverable. (low grade zinc resource is estimated at 1.53 billion pounds of indicated zinc metal)
* A mining and metallurgical flow sheet that will recover silver, zinc, and potentially lead
* Greater than 98% recycling of cyanide via the SART process -- Cyanide is one of the most expensive reagents used in the leaching process, so the recycling of this will have a significant positive effect in lowering the overall costs. (bolded for emphasis)
* Room to optimize and improve recoveries to 75%-80%
SUMMARY OF SILVER METALLURGICAL TEST WORK
Test work on leaching the silver ore at Sierra Mojada has been conducted by KCA. Work has focused on cyanide leach recovery of the silver, and zinc and copper, using "Bottle Roll" tests to simulate an agitation leach system common on many mine sites.
Samples have been taken separately from drill core, mineralized outcrop, and trenches from the "Centenario", "Fonteriza" and "Shallow Silver" Zones of the deposit and have been crushed and mixed to create either a "composite" sample representative of each of the 3 zones, or a series of composite samples based on the silver grade for each of the three zones.
SUMMARY OF SILVER RESULTS
A summary of results for the cyanide leach test work on silver recovery is shown in the table below.
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Leach
Target Solution Calculated
KCA p80 NaCN Head,
Sample Size, Conc., gms % Ag
No. Sample Description mm g/L NaCN Ag/MT Recovery
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64605 Centenario, Composite No. 5
(10 to 20 gms Ag/MT) 0.074 5.0 16.9 76.7%
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64601 Centenario, Composite No. 1
(10 to 20 gms Ag/MT) 0.074 5.0 17.5 68.5%
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64602 Centenario, Composite No. 2
(20 to 30 gms Ag/MT) 0.074 5.0 23.3 69.6%
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64606 Centenario, Composite No. 6
(20 to 30 gms Ag/MT) 0.074 5.0 24.6 76.2%
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65609 Centenario, Composite No.
9; (30 to 60 gms Ag/MT) 0.074 5.0 41.6 81.8%
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65441 Centenario, Composite No.
7; (30 to 60 gms Ag/MT) 0.053 1.0 42.6 85.0%
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64603 Centenario, Composite No.
3; (30 to 60 gms Ag/MT) 0.074 5.0 43.3 81.8%
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65610 Centenario, Composite N0.
10: (approx. 100 gms/MT) 0.074 5.0 104.0 79.0%
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64604 Centenario, Composite No.
4; (greater than 60 gms
Ag/MT) 0.074 5.0 105.8 88.4%
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65608 Centenario, Composite No.
8; (greater than 60 gms
Ag/MT) 0.074 5.0 172.4 89.0%
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65743 Fronteriza, Composite No.
1; (35 to 50 gms Ag/MT) 0.044 10.0 43.6 51.0%
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65744 Fronteriza, Composite No.
2; 50 to 100 gms Ag/MT 0.045 5.0 67.4 55.0%
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65745 Fronteriza, Composite No. 3
(100 to 150 gms Ag/MT) 0.040 5.0 126.2 60.0%
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65746 Fronteriza, Composite No. 4
(150 to 200 gms Ag/MT) 0.038 10.0 182.9 62.0%
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65747 Fronteriza, Composite No. 5
(200+ gms Ag/MT) 0.053 20.0 597.0 86.1%
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63604 Shallow Silver Zone, Core
Composite 0.053 20.0 57.6 70.7%
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65770 Shallow Silver, Composite
No. 2 (45 to 100 gms
Ag/MT) 0.053 20.0 65.8 68.2%
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65771 Shallow Silver, Composite
No. 3 (100 to 150 gms
Ag/MT) 0.053 20.0 110.1 68.7%
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AVERAGE 73.2%
Observations from these results include;
• Silver recoveries generally show an increase with higher grade.
• Silver recovery is grind size sensitive with finer grinds giving higher recoveries.
• Due to high cyanide soluable zinc values, cyanide concentration is critical to maximize silver recovery.
Work will continue to optimize the parameters for leaching the silver, with the average silver recovery expected to reach 75%-80% as test parameters are optimized.
SUMMARY OF THE ZINC RESULTS
In addition to the tests assessing the silver recoveries via cyanidation, KCA performed cyanide leach tests to determine the recovery of the "low grade" zinc to the leach solution. The following two tables provide the results of the zinc recoveries to cyanide solution in the cyanide leach tests.
Zinc Recoveries
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Target Average Head, Avg. Tails, Zn Extracted,
Sample Description NaCN, gpL Zn, mg/kg Zn, mg/kg %
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Shallow Silver Zone 10 7,750 4,380 41%
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Centenario 10 2,080 1,540 26%
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Fonteriza 10 18,870 7,359 64%
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Average All Tests 44%
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It should be noted that the zinc recovery was still climbing at the end of the majority of the leach tests, indicating that higher zinc recoveries are possible if higher cyanide concentrations are used. Silver recoveries are also expected to increase with higher cyanide concentrations.
THE SART PROCESS:
The purpose of the "SART" process (Sulfidization, Acidification, Recycling and Thickening) is to;
1.Regenerate and recycle the cyanide used in the leaching process of the silver, and zinc -- thereby significantly lowering cyanide costs -- one of the major costs in any leach process.
2.Recover the zinc as saleable sulphide concentrates. Selling this concentrate will contribute significantly to reducing the net operating costs of the SART circuit.
The studies were performed at BioteQ utilizing the leach solution samples collected at KCA after the silver had been precipitated out of the solution. Testing was conducted at a laboratory bench top scale using batch testing methods to assess the effectiveness of different process conditions. The tests were conducted using sodium hydrosulphide (NaHS) and hydrogen sulphide gas (H2S) as sulphide reagent sources. Test results provided values for cyanide recovery, and zinc and copper recovery to sulfide concentrates. The tests proved very successful and the results are summarized in the discussion below by BioteQ.
The following were concluded after analyzing the experimental data for various reaction conditions:
• Recovery of WAD cyanide to free cyanide was close to 100% under operating conditions.
• Zinc can be recovered from the barren leach solution (BLS) using both sulphide sources (NaHS and H2S).
• Zinc grade of the concentrate is predicted to be between 63%-64%, considered a high-grade zinc sulphide product.
• The small amount of silver that was present in the BLS was removed from solution to below detection limit of the analytical equipment and reported to the metal sulphide solids.
MINING FLOW SHEET FOR THE SILVER MINERALIZATION AT SIERRA MOJADA
Figure 1. Mining flow sheet for silver mineralization at Sierra Mojada
TESTWORK ON THE LEAD
Floatation testwork on the lead mineralization is currently underway. With over 537 million pounds of contained lead metal, the lead has the potential to provide significant upside to the project. The ore containing the lead mineralization will already have been milled and will only need to be passed through a floatation cell either prior to vat leaching or after vat leaching on the way to the tailings dam.
Tim Barry, President, CEO and director of Silver Bull states, "We are extremely pleased with the results of the metallurgical program. Work going forward on the metallurgy will now focus on optimizing and improving the silver and low grade zinc recoveries at various steps along the process, and examining the potential to extract more value from lead and zinc. By unlocking the metallurgy we have taken another major step forward in development of one of the largest undeveloped silver resources in Mexico. The next step for the company is a Preliminary Economic Assessment which we expect to have out to the market in the third quarter of this year."
THE NEXT STEPS GOING FORWARD
• Cyanide leach tests will continue on the silver, low-grade zinc and copper ore to optimize recovery and leach time. Drivers to improve recovery will include stronger cyanide solutions, grind size of the ore, and leaching residence times.
• Floatation tests on the lead mineralization
• Floatation tests are also underway on the "high grade" zinc (>8%) mineralization which sits underneath the silver mineralization at the eastern end of the deposit.
About Silver Bull: Silver Bull is a well funded US registered mineral exploration company listed on both the NYSE MKT and TSX stock exchanges and based out of Vancouver, Canada. The flag ship "Sierra Mojada" project is located 150 kilometers north of the city of Torreon in Coahuila, Mexico, and is highly prospective for silver and zinc. Silver Bull also has 2 mineral licenses in Gabon, Central Africa, which are prospective for gold, manganese, and iron ore.
The technical information of this news release has been reviewed and approved by William J. Pennstrom, Jr., a qualified person for the purposes of National Instrument 43-101. Mr. Pennstrom, a consulting process engineer and President of Pennstrom Consulting, Inc. has acted as the Qualified Person, as defined by NI 43-101, for evaluation of the metallurgical testing data. He has over 30 years of experience in mineral process design and operation, and has been an independent process and metallurgical consultant for the mining industry for the last 12 years. He is a Registered Member of the Society of Mining, Metallurgy and Exploration (SME Member No. 2503900). Mr. Pennstrom and Pennstrom Consulting Inc. are both independent of the Company under NI 43-101.
On behalf of the Board of Directors
"Tim Barry"
Tim Barry, MAusIMM
Chief Executive Officer, President and Director
INVESTOR RELATIONS:
Matt Hallaran
+1 604 336 8096
info@silverbullresources.com
http://www.silverbullresources.com/s/news.asp?ReportID=590659
Dan 
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