Gold glitters at Twin Hills
While continuous drilling is likely to further increase the mineral resources at TSX listed Osino Resources’ gold project in Namibia, the company is fast-tracking development at Twin Hills, about 25km from the town of Karibib.
By Leon Louw, owner and editor of WhyAfrica
Osino published a preliminary economic analysis (PEA) on Twin Hills in August 2020 and is in the process of working towards a pre-feasibility study (PFS) based on an updated mineral resource estimation (MRE). Early drilling results at Twin Hills were extremely positive and indicate that Osino is on track to become one of the most exciting new gold mining projects in Southern Africa.
Osino expects to complete some additional infill and step-out drilling before the end of May 2022 which will convert more of the current Inferred resources to the Indicated category and allow the material to be added to the PFS mine plan.
Heye Daun, Osino’s President & CEO is confident that Twin Hills’ mineral resource endowment will continue to grow. “We have commenced with Indicated resource conversion drilling at Clouds and Twin Hills West, and follow-up drilling of the recently discovered high-grade shoots at Twin Hills Central and Clouds. We are also planning additional down-dip step-outs along the spine of these deposits and believe that once completed, drilling should result in another significant resource upgrade.”
Twin Hills is an orogenic-style, sedimentary-hosted, structurally controlled gold project contemplated as an open pit. Osino has completed 186,826m of Reverse Circulation (RC) and Diamond Drilling (DD) at Twin Hills since the discovery in 2019 of which approximately 167,597m was included in the recent MRE update up to the data cut-off date of 19 February 2022. Since then, more than 19,229m of additional RC and DD drilling was completed.
In addition, Daun says that the drilling team at Osino has completed about 3000m of grade control orientation drilling (12.5m x 12.5m) at Twin Hills Central in March 2022.
“The aim of this drilling is to better define the short-range variability of the THC mineralisation. This grade control exercise may potentially enable more advanced geostatistical resource estimation techniques to be applied (uniform conditioning versus ordinary kriging) to the Twin Hills mineral resource. The aim of this exercise is to model the effects of selective mining with the aim of potentially improving the processing head grade,” says Daun.
Drilling is ongoing with six DD and three RC rigs. While assay results for most of this drilling are outstanding, it is expected that the drilling will be completed during May 2022 with all assays received within 4-6 weeks of completion of drilling.
Development Study Update
Several studies to complete the PFS at Twin Hills are underway with many at an advanced stage. Lycopodium Minerals Canada were retained by Osino with responsibility for the overall management of the Twin Hills Project PFS. This comprises study management, cost estimating, management of metallurgical testwork and coordination and preparation of the Technical.
The Twin hills project is located in a semi-arid area with seasonal rainfall and recurring droughts where surface water is limited. With the growth in mineral resources and likely higher future processing plant throughput, Osino expects the Twin Hills projects’ water demand to increase.
For this reason, the company favours dry-stack tailings despite its higher capital cost. A trade-off analysis is underway to determine the most cost-effective and appropriate tailings deposition strategy for the project.
Twin Hills is about 25km from Karibib, and the neighbouring Navachab Gold mine, both of which are supplied with bulk water by Namibia’s water parastatal, Namwater, via pipeline from Swakoppoort dam. Supplies from this source are however limited due to seasonal rainfall.
Osino commissioned two specialist Namibian consultants, Knight Piesold and SLR Consulting, to carry out the necessary hydrological studies and drill programs to develop their own water sources for the Twin Hills project.
Water provision will be based on ground water abstraction from existing, nearby marble aquifers on a sustainable yield basis, the development of sand aquifers using ground weirs in the nearby, ephemeral Khan River system and additional augmentation using piped water (effluent and fresh) from the nearby town of Karibib.
A total of 40 hydrological assessment and water abstraction boreholes have been drilled within the Twin Hills mining area since 2019, with a demonstrated combined water yield of 168m3/hr or 1.49m m3/year. Total mine make-up water demand at an assumed 4.5mtpa processing capacity is approximately 1.5m m3/year which will be supplied from several boreholes in the area.
Twin Hills only 20 km from the existing substation and grid power supply to the neighbouring Navachab gold mine. Namibia’s parastatal bulk power utility, Nampower, also has plans to construct a new substation in Karibib (the Erongo substation) which will enable the supply of sufficient grid power to Osino’s Twin Hills project and other consumers in the region.
In March 2022 Osino signed a power-supply agreement with Nampower for a 16MW grid connection to the planned Erongo substation. Depending on the final processing plant capacity, Twin Hills maximum power demand is expected to grow to approximately 20MW, and discussions with Nampower have commenced to amend the power-supply agreement to cater for the additional expected demand.
Under the terms of the contract the grid power supply is subject to a 36 to 48-month Nampower procurement and construction lead time from signature ( March 2022).
Discussions are currently underway to shorten this procurement period. In addition, investigations are ongoing to procure contingency power sources to bridge any potential supply gaps. Daun says that Osino expects to have the required power available when full production commences.
Osino has also engaged a local Namibian electrical engineering consultancy to assist in designing and procuring large-scale photovoltaic power supply in addition to grid power. Various attractive proposals have been received and are being investigated further.
Osino Resources’ Twin Hills project is one of about 30 project sites that WhyAfrica will visit in July as part of the WhyAfrica Southern African Road Trip. Follow WhyAfrica on social media and subscribe to our newsletters and magazines to get up to date information about this exciting trip and concept.
Leon Louw is the founder and editor of WhyAfrica. He specialises in natural resources and African affairs.
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