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Heva-Hosco (Joanna) Project

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Mine TypeOpen Pit
  • Gold
Mining Method
  • Truck & Shovel / Loader
Mine Life... Lock
SnapshotThe property consists of two separate deposits: the free-milling Heva deposit and the refractory ore Hosco deposit. Minimal work has been done on these deposits since 2014. Pending further information, the analysis provided assumes a tentative start date of 2025.


Hecla Mining Company 100 % Indirect



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Deposit type

  • Vein / narrow vein


The Joanna Property is situated on the famous Cadillac structural break. The structure generally strikes east-west and dips northward. It is characterized by a layer of schistose, chloritic rocks cross cutting a uniform package of metamorphosed, fine-grain sediments. Gold mineralization is composed of disseminated sulphides (pyrite, arsenopyrite and pyrrhotite) in deformed and biotite-rich zones along the Cadillac Fault. Small quartz veins ranging from a few centimetres to a metre wide are encountered in these zones. The Au disseminated mineralization is found in strongly altered and deformed corridors with an azimuth of N260° dipping 55° to the north-west. These mineralized corridors average a horizontal width of 20 metres and extend along the strike over 3,000 metres, reaching a depth of 400 m.

Gold mineralization of the Hosco-Heva area is distributed in multiple lenses on both sides of the Cadillac Fault, making each one a few metres to a few tens-of-metres thick. To date, mineralization has only been identified in the Fault zone. The more continuous and gold-rich zones seem to be associated with a silica-biotite, albite and tourmaline alteration. Mineral assemblage also includes variable concentrations of white mica, chlorite carbonate, garnet and possibly other alumino-silicates. Amphibole and tourmaline rich replacement zones have been locally identified. In the Heva zone, gold mineralization contoured this type of alteration zone. Mineralized lenses are included within a 100 to 190 metre wide lower grade halo of 0.5 to 2.0 grams per tonne.

Generally speaking, most of the zones look alike in terms of structure and mineralization, some differentiate slightly by the content in quartz veins (millimetric to centimetric), arsenopyrite, pyrrhotite, and pyrite but currently they are believed to be all related to the same geological event with variations in the alteration assemblages and degree of deformation. Narrow, widely spaced, quartz veins with higher grades have been intersected on the Heva side and immediately south of the Hosco Zone.

Gold is concentrated in different locations closely related to sulphides grains and is mostly fine grain (<20 micro metres). According to different petrographic and micro-analytical studies performed on rock samples and on a sulphide concentrate sample, the majority of gold weight is under the form of free or attached particles to the surface of sulphides grains. A fraction of gold including sub-microns particles and ionic gold is concentrated in some types of arsenopyrite grains.

Gold in the Hosco deposit is closely associated to sulphides and alteration mineral distribution indicating at first view the prime of hydrothermal reaction with hosted sediments. The microscopic in- situ observation of gold particles or concentrations in many alteration contexts and gold enrichment levels suggested that the sulphidation process was the main process involved in the gold precipitation process.

Gold in the deposit is mostly microscopic with a few occurrences of coarser, sub-millimetric particles. Thin section and sulphide concentrates microscopic observation returned a majority of very fine grain particle (average of 8 µm in the concentrate) and about 30% of gold weight is evaluated to be under a colloidal or solution state in sulphides grains. In-situ measurement of gold concentration in individual sulphide grains by SIMS (Secondary Ion Mass Spectrometry) returned gold concentrations at different levels in all groups of sulphides. The maximum average gold grade was obtained in coarse arsenopyrite with 80 g/t. On the other hand, pyrite and pyrrhotite contain about 1 g/t gold (SGS Lakefield 2008).

Apparent zoning of sulphide assemblages across the deposit seems to be related to the fault position. Pyrrhotite, which covers the whole deposit, is mostly concentrated at both edges of the mineralized system with a strong concentration inside the ductile portion of the fault zone. The main concentration of arsenopyrite is located inside a few ten to hundred meters south of the fault where the most consistent grades are found. Pyrite, usually unnoticeable, is restricted to a narrow portion of the mineralized system immediately south of the fault. According to microtextures, all sulphides are contemporaneous.

The mineralized corridor extends along a 2,450 m east-west trend and can be followed down to a depth of 400 m. Mineralized zones within that corridor dip by 50° to 65° to the north with a western plunge.

Gold is located in several lenses in the south side of the Cadillac Break dipping approximately 60 degrees to the north and forming an envelope of thickness between 30 and 60 metres. In the Heva area, main lenses (Zone P) are located on the footwall contact of the Cadillac Fault up to 30 metres from this fault. Mineralization takes the form of a swarm of centimetric to metric grey/white quartz veins within biotite-tourmaline altered wacke and argilite. Pyrrhotite is the main sulphide. Locally, gold is remobilized inside the chlorite schist of the Cadillac Fault (Zone F). Others lenses (Zone S) are developed in amphibolitized conglomerate between 70 to 110 metres from the fault zone footwall.

Heva East
Approximately 1 kilometre east of the Heva sector, mineralization has been intersected between 10 to 60 metres from the Cadillac Fault footwall. Gold is associated with strong concentrations (up to 20%) of pyrrhotite inside amphibolitized rocks of unknown origin. Heva East is a new mineralized area, intersected to date along a 200 metre strike and with a possible extension open in all directions.

Heva West
High grades have been intersected in this area. Arsenopyrite is mainly associated with quartz/tourmaline veins in silicified, sericitized and biotized rock. These zones are located at least 125 metres from the footwall contact of the Cadillac Fault. Mineralized zones in this area are usually narrower than main lenses (Zone P) located on the footwall contact of Cadillac Fault.



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CommodityUnitsAvg. AnnualLOM
Gold koz 1091,454
All production numbers are expressed as metal in doré.

Production Costs

Cash costs Gold USD 716 / oz *  USD
Assumed price Gold USD 1,350 / oz *  USD
* According to 2012 study / presentation.

Operating Costs

OP mining costs ($/t mined) CAD 11.9 *  CAD
Processing costs ($/t milled) CAD  ....  Subscribe
Total operating costs ($/t milled) CAD  ....  Subscribe
* According to 2012 study.

Project Costs

MetricsUnitsLOM Total
Initial CapEx $M CAD  ......  Subscribe
Sustaining CapEx $M CAD  ......  Subscribe
Closure costs $M CAD  ......  Subscribe
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OP OpEx $M CAD  ......  Subscribe
Processing OpEx $M CAD 508.3
Refining and transportation $M CAD  ......  Subscribe
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Royalty payments $M CAD  ......  Subscribe
Gross revenue (LOM) $M CAD  ......  Subscribe
Pre-tax Cash Flow (LOM) $M CAD  ......  Subscribe
Pre-tax NPV @ 0% $M CAD  ......  Subscribe
Pre-tax NPV @ 5% $M CAD  ......  Subscribe
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Required Heavy Mobile Equipment


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Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Mar 4, 2024
....................... Subscription required ....................... Subscription required Subscription required Mar 4, 2024


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