Twin Hills Gold Project Overview

The Twin Hills Gold Project is located within Namibia’s prospective Damara Orogenic Belt, in proximity to and along strike of the producing, open-pit Navachab and Otjikoto gold mines.

Twin Hills is a sedimentary-hosted, structurally controlled gold deposit that fits the broad orogenic lode gold model and is amenable to conventional open-pit gold mining and carbon-in-leach metallurgical processing.

In September 2022 a prefeasibility study (“PFS”) was prepared by Lycopodium Minerals Canada (“Lycopodium”) in accordance with National Instrument 43-101—Standards of Disclosure for Mineral Projects (“NI 43-101”) and contemplates a low-risk, technically simple open-pit mine utilizing contract mining and feeding a conventional carbon-in-leach (“CIL”) metallurgical plant processing 5 million tonnes of mineralized material per annum.

Project Location

The Twin Hills Gold Project (the “Project”) is located in central Namibia approximately 150 km northwest of the capital city of Namibia, Windhoek and is owned by Osino Resources Corp. (“Osino”) through a number of its local subsidiary companies. The Project is comprised of 11 exclusive prospecting licenses (“EPLs”) granted by the government of Namibia, which are held over a combined area of 153,206 ha in and around the regional towns and settlements of Usakos, Karibib, Omaruru, and Wilhelmstal in the Erongo Region of Namibia as shown in the figure below.

Twin Hills Discovery History

The Twin Hills Gold Project lies within the Kuiseb Formation, a sequence of turbiditic marine sediments several kilometres thick, which was folded during the neo-Proterozoic Damara orogen between 520 and 500 Ma. The gold mineralization is hosted within a meta-greywacke unit, which has been tightly folded into an overturned syncline, underlain by biotite schist and cordierite schist.

The discovery and growth of Osino’s flagship Twin Hills gold deposit in 2019 is a telling story of hard work, perseverance and not following accepted dogmas regarding prescriptive geological models. It demonstrates the use of innovative sampling techniques to enhance the identification of targets for follow-up drilling. 

Between 2016 and 2017 David Underwood and Jon Andrew, Osino’ founding pair of exploration geologists, undertook a review of Osino’s exploration strategy which resulted in shifting Osino’s focus away from the known small deposit scale prospects to potentially much larger,  district-scale prospects by exploration targeting using fundamentals of orogenic gold deposits. The key regional features/criteria of the orogenic gold model, and how they relate to the Namibian and Damara Orogenic Belt setting, are as follows:

•     Very large, long-lived fault structures e.g. those found within the Omaruru and Otjohorongo Lineaments and the recently identified Karibib Fault;

•     Large sedimentary and volcanic basins as a source of fluids;

•     Compressional tectonics, which are required for pumping the fluids out of the basins and through these large 1st order structures;

•     Zones of structural and lithological complexity along 2nd and 3rd order structures acting as trap sites for metal enriched hydrothermal fluids.

•     Multiple associated gold occurrences across the target.

This review entailed a re-interpretation of the regional structural framework and identification of prospective structures and potential traps under cover, initially using the public domain, high-quality government magnetic dataset. This resulted in the identification of the regional-scale Karibib Fault Zone and an early recognition of its large-scale mineralising system potential and the vectors that ultimately lead to the discovery of the Twin Hills gold system through thick cover.  



Regional soil sampling identifies the Karibib Gold Trend (~20km gold in soil anomaly), coincident with the regional Karibib Fault Zone.


Drill testing of outcropping gold mineralisation along the Trend suggests gold values increase to the west with best results at Twin Hills East; soil sampling ineffective to the west of this due to sand and calcrete cover.


Calcrete sampling (the first of its kind in Namibia), defines a coherent anomaly west of Twin Hills East, extending the Karibib Gold Trend (> 30km) and bedrock drilling confirms gold anomalism in the bedrock schists (> 20m calcrete cover in places).


Definition of Twin Hills Central, Twin Hills West and Clouds targets from calcrete sampling and shallow percussion drilling, all associated with ground magnetic anomalies.


Initial diamond drill program (7 holes, ~1,480m) confirms thick low grade gold mineralisation; Twin Hills Discovery confirmed with 800m strike length of mineralisation (26 September 2019), strike length quickly increased to 1,200m and bedrock mineralisation confirmed at Twin Hills West and Clouds.


First large scale resource definition and growth drilling campaigns (> 50,000m), completed Induced Polarization (IP) survey defining new targets, discovery of Clouds mineralisation.


PEA released with Maiden Mineral Resource Estimate (MRE) at Twin Hills; 13.5 Mt at 1.00 g/t Au for 0.43 Moz (Indicated) and 42.6 Mt at 1.08 g/t Au for 1.47 Moz (Inferred).


Mining license application submitted, brownfields discoveries at Oryx North, Oryx South and Kudu lobes, completion of 121,000m drilling for the year.


Upgraded MRE at Twin Hills, now a total of 2,72 Moz (Indicated and Inferred), discovery of Clouds West.

H2 - 2022

Significant increase in MRE at Twin Hills, now > 3 Moz Au; 81.3 Mt at 1.08 g/t Au for a total of 2.83 Moz (Measured & Indicated) and 7.2 Mt at 1.05 g/t Au for a total of 0.24 Moz (Inferred), based on > 210,000m of drilling.


Prefeasibility study (“PFS”) for Twin Hills outlines a 13+ year mine life with life-of-mine production of 169,000 ounces per annum.


DFS on track for anticipated delivery in Q2, updated met testwork and trade-off analyses completed, capex estimate underway, updated mineral resource estimate to be completed with DFS.


Ongoing focus on growth and new discovery.

Mineral Resources

The maiden drill program consisted of 7 diamond drill holes located along 3 fence lines about 400m apart with 100m hole spacing. The program was designed to test bedrock gold anomalies covered by a thick layer of calcrete which were with a large magnetic and soil & calcrete anomaly which had been delineated earlier in 2019. 

This initial drill program was a resounding success with 5 of the 7 holes intersecting significant mineralization open in all directions. 

The best gold intercepts from Phase 1 included:

  • 104m @ 0.70 g/t Au (from 115m), incl. 10m @ 1.27 g/t and 20m @ 1.11 g/t
  • 189m @ 0.69 g/t Au (from 21m), incl. 14m @ 1.14g/t, 7m @ 1.42g/t and 5m @ 1.43g/t
  • 78m @ 0.64 g/t Au (from 91m) incl. 23m @ 1.01g/t
  • 65m @ 1.37 g/t Au (16 – 81m), incl. 31m @ 2.2g/t (42-73m)
  • 17m @ 2.17g/t Au (116 – 133m), 11m @ 1.76g/t Au (165 – 176m), 6m @ 1.29g/t Au (182 – 188m), 7m @ 1.10g/t Au (16 – 23m) and 3m @ 2.73g/t Au (87 – 90m)
Figure 1: Twin Hills Gold Project: > 225,000m Drilled since discovery in 2019

The PFS is based on the previously reported Mineral Resource block model reported on 9 August 2022, using a cut-off grade of 0.3g/t Au, resulting in a Measured and Indicated Mineral Resource of 81.3 Mt at 1.08g/t Au for a total of 2.83 Moz and an Inferred Mineral Resource of 7.2 Mt at 1.05g/t Au for a total of 0.24 Moz. 

A total of 212,184m of drilling from 1,016 holes (125,722m of diamond core from 451 holes and 86,462m of RC drilling from 565 holes) has been completed at Twin Hills since 2019 and was used for the Mineral Resource estimate.

Mineral Resource Statement

The mineral resource is that material within the reporting pit shell above a 0.3g/t Au cut-off grade. The mineral resource estimate (“MRE”) has an effective date of July 25, 2022 (see table), and a corresponding technical report disclosing the mineral resource estimate in accordance with NI 43-101 was prepared for the Company by Mr. Anton Geldenhuys of CSA Global (Pty) Ltd. (“CSA”), who is an independent qualified person under NI 43-101. The Company has filed the technical report on SEDAR under its profile at

Table 1: Mineral Resource for the Twin Hills Gold Project at a 0.3g/t Au cut-off as July 25, 2022

Notes on mineral resource reporting:

  1. Figures are rounded to the appropriate level of precision for the reporting of mineral resources. Mineral resources are stated as in situ dry tonnes. All figures are in metric tonnes.
  2. The mineral resource are classified under the guidelines of the CIM Definition Standards for Mineral Resources and Mineral Reserves and adopted by the CIM Council, and procedures for classifying the reported mineral resources were undertaken within the context of the Canadian Securities Administrators NI 43-101.
  3. The mineral resource is reported within a conceptual pit shell determined using a gold price of US$1,800/oz and conceptual parameters and costs to support assumptions relating to reasonable prospects for eventual economic extraction:
  4. 4% royalty (3% government royalty and 1% export levy)
  5. Selling costs of US$2.75/oz Au
  6. Mining costs of US$2.00/t mineralized material and US$1.85/t waste, with additional cost attributed to depth below surface
  7. Processing and rehandling costs of US$8.15/t run of mine mineralized material
  8. G&A cost of US$4.00/t run of mine mineralized material
  9. Slope angle of 48° in weathered rock and 55° in fresh rock
  10. 90% recovery of Au from CIL circuit
  11. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
  12. The exclusive prospecting licenses (“EPL’s”) on which the mineral resource is reported, are 90%, 100%, 95% and 90% owned by Osino. As a result, the blended ownership of the total reported gold ounces attributable to Osino is 94.5%. The Company has entered into agreements to acquire the minority interests to increase Osino’s ownership to 100% (see Osino news release dated August 16, 2022).

PFS Overview and Financial Analysis

The PFS was prepared in September of 2022 by Lycopodium Minerals Canada in accordance with National Instrument 43-101—Standards of Disclosure for Mineral Projects (“NI 43-101”).

The table below summarizes the results and key valuation metrics of the PFS on a pre- and post-tax basis.

Table 2: Prefeasibility Study Economic Assessment Summary

The financial model was completed on a 100% project basis and includes a 3% gross royalty and 1% export levy to the Namibian government. The economic analysis carried out for the Project uses a cash flow model at a base gold price of US$1,700/oz and a 5% discount rate.

A sensitivity analysis utilising a range of gold prices and operating variables was completed.

Mine Design and Production Schedule

Inferred resources were excluded from the pit optimisation runs and the Reserve statement and were classified as waste during the LOM production schedule runs. The deposit is a large, shallow gold deposit that is amenable to bulk open pit mining.

Figure 2: Design, Layout and Location of Process Plant, Pit and Waste Rock Dumps

The project is planned as a multi-pit mining operation, as shown in Figure 2, with seven pushbacks in the Twin Hills Central / Bulge pit design and three separate satellite pits (Clouds, Clouds West and Twin Hills West) to be mined in different phases throughout the LOM. The pit design and scheduling has been undertaken to allow for interim pushbacks which will be mined early, thereby allowing higher grade to the plant to be maximised in the early years, and waste stripping deferred as far as possible into the future.

Plant Mineral Processing

The Twin Hills process plant will have a nameplate capacity of 5.0 Mtpa of ore and a nominal capacity of 649 tonnes per hour (tph).

Gold recovery will be achieved using a 3-stage crushing, ball milling, gravity, pre-oxidation, carbon-in-leach (“CIL”), cyanide detoxification and tailings thickening and filtration process plant flowsheet. The process is based on conventional unit operations well proven in the industry and will achieve high recoveries from all major rock types that are planned to be processed.

The detailed plant flow diagram is depicted in the Figure below.

Figure 3: Schematic Process Plant Layout

Site Location and Infrastructure

The Twin Hills Project is in central Namibia approximately 20km’s from the local town of Karibib, and 150km from the capital city, Windhoek. The Project area has access to excellent infrastructure by being in close proximity to Namibia’s well-maintained national rail, road and bulk utilities network.

The Project is located within 5km’s of the sealed national highway network, within 20km’s of a major high tension overhead power line and within 220km’s of the modern seaport of Walvis Bay, to the west of the Project, which is the main logistical port supplying the mining industry in the region. The Project is also within 30km’s of the well-established Navachab gold mine, which has been in consistent production since 1989.

Proposed Project Development Plan

Osino’s intention is to continue to fast-track the development of the Twin Hills Gold Project. The Company is proceeding with a definitive feasibility study (DFS), anticipated to be completed in H1 2023.  The study will be based on the flowsheet and design concepts developed for the PFS. A major deliverable will be cost estimates with an accuracy range of approximately ± 15% based on further development of the engineering designs.