Lens-like zones of mineralization, largely in brecciated tops of amygdaloidal Precambrian basalt lava flows, consist mostly of primary chalcocite accompanied by small amounts of native copper and native silver. Silver in the copper-bearing zones varies mostly from 1-15 g/tonne Ag. Traces of other sulfide minerals are also present. Mineralization comes to the bedrock surface and is covered by 3 to 30 meters of glacial deposits. The 543S deposit is in the western portion of a 20-mile long belt of chalcocite prospects that extends east from a belt of large native copper mines, centered near the town of Calumet, Michigan, that were mined for about 130 years before closing in 1968 due to low copper prices.
The 2012 drill holes are within an area of 101 historic diamond drill holes called the 543S sulphide deposit, a zone of chalcocite mineralization that was explored from 1973-1977 and briefly in the mid-nineties. The 543S deposit contains a historic resource estimate of 4.5 million short tons averaging 2.27% Cu at a 0.75% Cu cut-off grade as described in a Technical Report by Behre Dolbear & Company, Ltd. titled "Centennial and Kingston Native Copper, 543S, and Other Copper Sulfide Properties, Houghton and Keweenaw Counties, Michigan, USA'' dated September 29, 2011. The historical resource estimate is contained in six separate lenses averaging 5.0 meters (16.5 ft.) true thickness that dip about 40 degrees to the north. The Company has not completed the work necessary to classify the historical estimate mentioned above as current mineral resources under Canadian National Instrument 43-101 ("NI 43-101"). The Company is not treating the historical estimate as current mineral resources as defined in NI 43-101 and the historical estimate should not be relied upon.
Highland's objective is to verify the non-compliant historic drill results with compliant assay data by reducing the historic drill hole spacing and twinning selected historic holes to establish a resource estimate compliant with NI 43-101. Resource modeling is expected to begin in early 2013.
Highland Exploration Program to Date
Current composite assay results from drilling are summarized in Table 1 (click here for link to Table 1). Drill hole locations are on Figure 1 at the end of this news release. Figure 2 is a cross section on line 500E that illustrates the continuity of mineralization at a 0.20% Cu cut-off (excluding silver). Additional sections were reported in earlier news releases. Summarizing progress to date at the 543S deposit:
Drilling start date - July 17, 2012Holes drilled - 164Meters drilled - 24,686Assays complete and released for - 98 holesMineralized intersections - 82 holesNo significant mineralization - 16 holesAverage thickness of all reported +0.20% Cu intersections per hole - 18.9metersApproximate lateral dimensions - 260 meters NW-SE by 600 meters NE-SWAverage grade of all reported +0.20% Cu composite intersections drilled byHighland:-- Numerical average for all drill holes - 1.77% Cu-- Weighted by cumulative length of composites in each hole - 1.57% Cu
The average thickness normally includes several separate mineralized lenses in each hole. The lateral dimensions indicated by Highland's drilling to date are similar to those reported in the Technical Report by Behre Dolbear & Company, Ltd., referenced above. The lower average grade of the composite intersections compared to the grade reported in the Technical Report is due to a lower cut-off grade (0.20% Cu) used by Highland compared to that used for the historic resource estimate (0.75% Cu) and to the unexpectedly long intersections in the interval 0.20-0.75% Cu that envelope the higher grade mineralization. Unmineralized holes are generally on the edge of the 543S deposit and are not included in the averages.