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Construction Site
Project Olza


In January 2013, Northcliff announced positive results from the Sisson Project Feasibility Study, including:

  • Pre-tax net present value (NPV) of $714 million at an 8% discount rate, an internal rate of return (IRR) of 20.4% and a 4.1-year payback on initial capital expenditures of $579 million.

  • Post-tax NPV of $418 million, IRR of 16.3% IRR and payback of 4.5 years.

  • 30,000 tonnes per day open pit mining and milling operation with an ammonium paratungstate (APT) plant, processing 281 million tonnes of ore over 27 year mine life at an average APT cash cost of $8.18 per tonne milled.

  • Average 557,000 metric tonne units (mtu) APT and 4.1 million pounds of molybdenum produced per year.

  • Mineral reserves as tabulated to the right.


January 2013 at $8.83/tonne NSR cut-off

Sisson Mineral Reserve.png


Sisson Site Plan

For further details see March 2013 Technical Report filed under the Northcliff profile at


A 3D block model was used as the basis for conceptual pit optimization using MineSight® software LG algorithm. This software, in conjunction with economic, metallurgical and geotechnical criteria was used to develop a series of economic pit shells which formed the basis for the detailed pit phased design and production schedule.

The Detailed Pit Design of the Ultimate Pit

For further details see March 2013 Technical Report filed under the Northcliff profile at

Sisson Pit Design of Ultimate Pit


Based upon the results of the 2013 Feasibility Study metallurgical test program, the process flowsheet for the Sisson Concentrator includes the following major processing steps:

  • Three stage crushing

  • Single stage, dual-line grinding and classification

  • Molybdenum rougher-scavenger and bulk sulphide flotation

  • Molybdenum regrind and four-stage cleaner flotation

  • Molybdenum concentrate dewatering and packaging

  • Tungsten rougher-scavenger flotation

  • Tungsten three-stage cleaner flotation

  • Reagent preparation and utilities

Sisson Block Flow Diagram

A Simplified Block Flow Diagram
for the Concentrator

For further details see March 2013 Technical Report filed under the Northcliff profile at


The Sisson property hosts a structurally-controlled deposit of tungsten and molybdenum that is genetically related to Late Devonian granite intrusions. The deposit comprises the contiguous I, II, III and Ellipse Zones, which obliquely span a north-trending, nearly vertical contact between two phases of the Howard Peak Granodiorite to the west and metavolcanic and metasedimentary rocks to the east. Significant mineral resources have been identified in Zone III and the Ellipse zone, both of which are open to further expansion.


Tungsten and molybdenum mineralization mostly occurs in narrow, sheeted, northwest-trending quartz-sulphide veins which surround larger, north-trending shear veins. Tungsten occurs predominantly in the mineral scheelite, and locally in wolframite, with molybdenum occurring in molybdenite. The near-surface Sisson deposit is amenable to open pit mining.

Sisson Mineral Resources.jpg


  1. CIM definitions were followed for Mineral Resources.

  2. Mineral Resources are estimated at a net smelter return (NSR) cut-off grade of US$9.00/t.

  3. Mineral Resources are estimated using a long-term metal prices of US$350 per mtu WO3 and US$15/lb Mo, and a US$/C$ exchange rate of 0.9:1.

  4. Metallurgical recoveries for the NSR calculation were 82% for Mo and averaged 77% for WO3 over the life of mine. WO3 recovery is a function of mill head grade.

  5. Numbers may not add due to rounding.

  6. The independent qualified person for the estimate is David Rennie, PEng., RPA, with an effective date of February 29, 2012.

For further details see March 2013 Technical Report filed under the Northcliff profile at

sisson Geology Mineralization

Mineral Reserves
Site Plan
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