Huckleberry Mines Ltd. (HML) is owner/operator of the Huckleberry copper. Imperial holds 100% of the shares of HML through HML Mining Inc., a wholly owned subsidiary of Imperial.
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Summary:
The Huckleberry mine is a typical porphyry copper-molybdenum deposit. It is characterized as a calc-alkalic coppermolybdenum type mineralization. These deposits are typically hosted in intrusive rocks, usually of granodioritic or quartz monzonitic composition, and in volcanic rocks surrounding intrusives. These deposits are often large, oval, inverted-cone shaped deposits, and display multiple zones of hydrothermal alteration and sulphide mineralization. The hydrothermal alteration is usually extensive and consists of an inner potassic zone closely associated with the sulphide mineralization, surrounded by propylitic alteration associated with pyrite. Phyllic and argillic alteration can be either part of the zonal pattern between the potassic and propylitic zones or can be somewhat irregular or tabular younger zones superimposed on older alteration and sulphide assemblages. Chalcopyrite, bornite, chalcocite, enargite, other copper minerals, molybdenum and pyrite are typically the dominant sulphides. The mineralization is dominantly structurally controlled, mainly through stockworks, veins, vein sets, breccias, disseminations and replacements.
Mineralization is similar in both the MZ and EZ deposits and is contained within altered volcanic rocks. Copper mineralization is predominantly chalcopyrite, occurring as fine to medium grained aggregate filling veinlets and fractures, and as fine grained disseminations in the envelopes around the veinlets. Molybdenum occurs as molybdenite, which is found as disseminations and clusters within quartz/gypsum veins. Molybdenite is generally low in chalcopyrite and appears to have been deposited separately and later than the copper mineralization.
The Main zone was the first zone to be discovered and was well defined by drilling. The zone was a kidney bean shape, wrapping around the east side of the porphyry stock with an arc length of 500 metre, a width of 150 m, and depths of up to 300 m below surface.
Mineralization in the EZ is easterly trending and about 200-300 m wide and 900 m long. Mineralization occurs to depths of over 300 m and remains open, however, the surrounding hills and unfavourable surface topography make it unlikely the deeper resource can be mined economically (note: pit has been backfilled). Core recovery was a problem in the upper portion of both deposits because gypsum fracture fillings have been dissolved, leaving the rock in a friable condition. Core recovery in this material has been as low as 0% over 100 m. Comparison of grade versus core recovery showed that grade fell off in proportion to recovery. Following an analysis of these comparisons, it was decided to consider all samples with recoveries below 50%, which only comprise less than 2% of the database, as unsampled. Assay data was composited on 8 metre vertical bench elevations. Specific gravity determinations were performed on 340 samples taken from eight holes within the EZ deposit. An average specific gravity of 2.69 was used for both deposits.
Gold, silver and molybdenum were not modeled in the Main zone due to incomplete data sets. Instead the block grades have been determined using correlations with copper assays, which are quite strong. For the EZ, molybdenum and silver grades were modeled using the Kriging parameters determined for the copper model. Due to the friable nature of the gypsum depletion zone, recognition of the overburden/bedrock face was difficult during the early drilling campaigns. The interface was established from drill data and the position of outcrops on the north slope and was used to estimate overburden thickness.
Production
On January 6, 2016, HML suspended pit mining operations. Stockpiles were then milled until the end of August 2016. Huckleberry mine remains on care and maintenance.
| Commodity | Units | 2016 | 2015 |
|
Gold
|
oz
| 1,927 | 3,576 |
|
Silver
|
oz
| 100,425 | 206,781 |
All production numbers are expressed as metal in concentrate.