Montero Mining and Exploration Ltd.

Montero Mining and Exploration Ltd.

April 13, 2015 09:00 ET

Montero's Bulk Leach Metallurgical Testing Returns 94% to 97% Total Rare Earth Element Recoveries at Wigu Hill Project

TORONTO, ONTARIO--(Marketwired - April 13, 2015) - Montero Mining and Exploration Ltd. (TSX VENTURE:MON) has received positive results from bulk leach testwork completed on three samples of REE bearing carbonatite dike material from Montero's Wigu Hill Project in Tanzania. Mintek reported that all samples returned very promising leaching efficiencies, with rare earth elements (REE) extraction recoveries of between 94% and 97% TREE (Total Rare Earth Elements). Initial hydrometallurgical testwork undertaken on similar mineralized material in 2011 (see news release - 29/11/2011) was successful in identifying a hydro-metallurgical 3-stage leaching process to extract the REE in solution.

Dr. Tony Harwood, President and Chief Executive Officer of Montero, commented; "Recently performed bulk leach metallurgical testwork returned excellent results with high leach efficiencies achieving recoveries of 94% to 97% TREE reported from REE bearing carbonatite dikes from Wigu Hill. Montero continues to seek a partner to advance Wigu Hill to a mining stage, similar to our phosphate project, which is funded to pre-feasibility and bankable feasibility study stage."

Montero has completed a series of mineral processing and hydrometallurgical testwork programs. Bulk samples of the bastnaesite-rich carbonatite were used by Mintek and SGS Laboratories for mineralogical analysis, mineral processing and hydrometallurgical testwork. Mineral processing testwork included x-ray sorting (see news release 01/02/2012) and froth flotation (see news release 29/7/2013) aiming to produce a high grade REE mineral concentrate. The principle focus for all test work programs is to develop an economic process to deliver saleable REE products and as such the hydrometallurgical testwork at Mintek has been successful in achieving this result.

Mintek developed a 3-stage hydro-metallurgical leach process and was asked to optimize this process. Additional sample material was sent to Mintek for this purpose and assaying of the bulk sample returned a value of 11.01% TREE.

The optimized results from Mintek on three samples concluded:

"The first stage is a gangue acid leach to reduce the carbonate content, which successfully reported approximately 55% mass loss for all the gangue leach tests done, but with minimal rare earth losses. The second stage (caustic crack stage) was successful in the removal of 71% of the silica in the samples, and the precipitation of the rare earths as hydroxides with minimal TREE losses. The third and final stage (a reductive acid leach stage) established that 94% to 97% of the TREE's can be recovered into the leach solution and from this, precipitation to provide a Mixed Rare Earth Oxide (MREO) concentrate for refining."

The final phase of the hydrometallurgical teswork is solvent and ion exchange to prepare individual purified REE products. Mintek has developed a rare earth solvent extraction pilot plant for this purpose and Montero has delivered a 1.5 tonne bulk sample to Mintek to further define the final stage REE extraction processing.

Montero's focus has been to establish the most efficient and economic mining and metallurgical extraction process in order to achieve margin and cash flow from the high grade REE mineralization at Wigu Hill. The fresh rock nature of the mineralization allows the use of conventional mineral concentration methods, which are showing successful results.

Drilling at Wigu Hill has delivered a NI43-101 compliant Inferred Resource Estimate (see news releases - 12/09/2011 & 06/08/2013) on the Twiga and Tembo Zones on the far-east flank and identified a number of mineralized zones across the full extent of Hill. Grab sampling, trench sampling and selected drilling has highlighted the more centrally located Nyati zone as having significant upside mineral potential, which needs to be substantiated by further infill drilling to expand the resource potential. Drill testing of this, and other known mineralized zones at Wigu Hill is still required.

Qualified Person's Statement

The technical information contained in this press release has been reviewed by Mr. Mike Evans, M.Sc. Pr.Sci.Nat., who is a qualified person for the purpose of National Instrument 43-101 and a consulting geologist to Montero.

About Mintek

Mintek, South Africa's national mineral research organization, has over 25 years experience in REE extraction and is one of the world's leading technology organizations specializing in mineral processing, extractive metallurgy and related areas. Working closely with industry and R&D institutions and reporting to the South African government's Minister of Mineral Resources, Mintek offers a complete range of process development services, from preliminary bench-scale investigations to large-scale piloting and integrated flow sheet development in support of bankable feasibility studies. Engineering design, plant construction and commissioning are carried out in conjunction with international partners. Comprehensive laboratory and piloting facilities for sample preparation, milling, flotation, physical separation, smelting, leaching, pressure leaching, and metal recovery and purification are supported by internationally accredited analytical laboratory and mineralogical services. For further information on Mintek, please visit

About Montero Mining & Exploration

Montero Mining and Exploration Ltd. is a mineral exploration and development company focused on bringing in a strategic investor or joint venture partner for the further development of the Wigu Hill Rare Earth Element Project in Tanzania. Montero's phosphate projects in South Africa are funded to pre-feasibility and bankable feasibility study stage by a strategic investor. The phosphate studies are for an integrated rock phosphate mine and fertilizer operation. Montero trades on the TSX Venture Exchange under the symbol MON.

Signed. Dr. Tony Harwood - President and CEO

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