Columbia Metals Corporation Limited

Columbia Metals Corporation Limited

August 23, 2005 17:34 ET

Columbia Metals Corporation Limited: Jojoba M + I In-Situ Resources 219,000 Ounces 'NI 43-101 Compliant'

TORONTO, ONTARIO--(CCNMatthews - Aug. 23, 2005) - Columbia Metals Corporation Limited (TSX VENTURE:COL) -


Further the Company's news release dated August 18, 2005, the Company provides the following information about the resource estimate summarized below.

Blakestad et al have re-calculated the mineral inventory for the northeast zone, the most prominent and best explored (and probably most readily exploitable) of the 7 known gold bearing zones on the property and classified them as mineral resources, which by definition, are not viable since an economic evaluation, a scoping study, or preliminary economic feasibility study has not yet been carried out for the known resources.

The following is extracted directly from the summary of Blakestad et al, August 12, 2005.

"The Mineral Resources reported in this document are provided in a range of gold cut-off values, categorized by grams per tonne gold (g/T Au) in-situ. A range of Indicated and Measured Mineral Resources (M+I) that correspond to the range of values potentially appropriate for development consideration of the Northeast Zone of the La Jojoba property are summarized below.

Tonnes greater Grade greater
than (1) Cutoff than (1) Cutoff
Au Cutoff --------------------------------
(g/T)(a) (tonnes) Au(g/T) Contained Ozs Au Cu (%)
0.25 10,590,000 0.682 232,208 0.06
0.3 9,050,000 0.752 218,808 0.06
0.35 7,910,000 0.813 206,759 0.06
0.4 7,070,000 0.865 196,623 0.07
0.45 6,270,000 0.922 185,864 0.07
0.5 5,510,000 0.984 174,319 0.07
1 equals greater than

The estimated M + I resources for the Northeast Zone are believed to be sufficiently defined to provide the basis for preparation of preliminary economic feasibility studies. It is recommended that a scoping study be performed to establish the basic design criteria and cost estimates for gold recovery. The scoping study should include a preliminary mine-pit design to accommodate the distribution of mineralization defined to date."

Additionally, at the 0.03 g/T Au cutoff grade, Blakestad et al report an additional inferred resource of 800,000 tonnes of 0.416 g/T Au (10,700 contained ounces) and 0.01% Cu.

Data verification was conducted by Blakestad et al, and the details are presented in their document, pages 22 through 35. A brief summary of which is as follows:

Previous operators, Minera Hecla S.A. de C.V., a wholly owned subsidiary of Hecla Mining Company ("Hecla") and Aquiline Resources Inc. ("Aquiline") conducted extensive programs of drill hole re-assaying, comprehensive data compilation and assimilation of previous work. Hecla drilled 6 core and 52 reverse circulation holes, conducted metallurgical tests and prepared a gold resource study. Aquiline produced two gold resource studies between 1994 and 1998. The principal author of the 43-101 Report, Blakestad states: "The principal author of this technical report was involved with exploration of the subject property during the Hecla Mining Company (Hecla) exploration phase in 1997, and at various times subsequently. He has first hand knowledge of the detailed review of prior exploration drilling on the property and has studied the geology, geochemistry, and drill records over an extended period of time. It is the writer's opinion that the integrity of the data compiled by Hecla-Aquiline and by unrelated third party companies is sufficient to meet the requirements of reporting resource estimates presented in this report."

The figures presented above are resource estimates and have not been subjected to economic consideration. Blakestad et al recommend preliminary economic feasibility studies in addition to metallurgical, rock quality, environmental, archaeological studies, as well as the above mentioned scoping study to provide the requisite in-put criteria for a preliminary feasibility study to determine potential economic viability.

Resource Estimate

The resource estimate for the northeast zone was performed by G. H. Giroux, P. Eng., MASc. with the results from 214 drill holes for which there were 13,326 assays for gold and 7,767 assays for copper.

A summary of some of the statistics derived by Giroux is presented below.

"It is noted that 75% or 10,188 gold assays are below 0.1 g/T. The coefficients of variation (standard deviation divided by mean grade) are relatively high indicating a high sampling variability.

The gold assays for La Jojoba formed a positive skewed distribution and a lognormal cumulative probability plot showed multiple overlapping lognormal populations (see Figure 9). Partitioning of this plot broke out 5 separate gold populations. Table 2 summarizes the parameters from these populations.

Table 2: Summary of Gold Populations

Population Mean Au (g/T) Proportion of Data Number of Samples
1 39.69 0.04 % 5
2 14.33 0.07 % 9
3 2.67 4.57 % 609
4 0.41 13.38 % 1783
5 0.02 81.94 % 10920

A cap level of 15 g/T Au was used to reduce the influence of the two upper erratic styles of mineralization. A total of 12 gold assays ranging up to 65 g/T were capped at 15 g/T Au."


The Northeast Zone was constrained between surface topography and a basement detachment fault. Drill holes within the Northeast Zone were compared to these two surfaces and those parts of drill holes that lay between them were subdivided into uniform 6 meter composites. Intervals at the lower boundary that were less than 3 meters were combined with the adjoining composite. A file of six plus or minus 3 meter composites was produced and the statistics for this data set are summarized in Table 4.

Table 4: Summary of six meter composite statistics for gold and copper

Au (g/T) Cu (%)
Number 2,403 1,650
Mean 0.35 0.038
Standard Deviation 0.77 0.108
Minimum Value 0.001 0.0005
Maximum Value 8.25 2.2
Coefficient of Variation 2.21 2.88

The combined effect of capping assays and smoothing over six meter intervals has reduced the coefficient of variation on both variables; by 52% for gold and 27% for copper.

Pairwise relative semivariograms were produced for gold and copper from six meter composites in the four principal horizontal directions, namely: azimuths 90 degrees, 0 degrees, 45 degrees and 135 degrees with dip angle 0 degrees. Anisotropy was demonstrated with different ranges in different directions for both gold and copper. Nested semivariogram models were fit to each direction with the longest ranges for both gold and copper between azimuth 45 degrees and azimuth 90 degrees. Directions between 45 degrees and 90 degrees were then tested with the longest range found at azimuth 052 degrees dip 0 degrees. An examination of the vertical plane perpendicular to this direction showed the longest range at azimuth 142 degrees with a -45 degrees dip angle.

The mineralization for the Northeast Zone was confined between the surface topography and the lower detachment fault. Lithologies within this area were all mineralized to varying degrees and there was no indication that lithology controlled the deposition of mineralization. Blocks 10m x 10m x 6m high were created and rotated with x-axis at azimuth 60 degrees.

Each block in the model was compared to the topography and detachment fault surfaces and the proportion of the block within mineralized material was recorded.

Giroux notes: "The resource estimate completed in 1997 (Giroux, 1997) used a 0.1 g/T Au interpreted shell to constrain kriging. The current estimate allowed the data to determine the grade within the area between surface topography and the detachment fault surfaces."

Ordinary kriging was used to interpolate grade for gold and copper into the block model. Kriging was completed in a series of passes using search ellipsoids oriented along the planes of anisotropy with progressively increasing dimensions.

A specific gravity (SG) of 2.70 was estimated by Hecla (Giroux, 1997) for converting cubic meters to tonnes. This number represented an average of 30 SG determinations obtained by Hecla from drill core. The results, as determined by McClelland Labs in Hermosillo, ranged in value from 2.40 to 2.9 with a mean of 2.70. For this study the average 2.70 was applied to all blocks.

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Contact Information

  • Columbia Metals Corporation Limited
    Carl Di Placido
    (416) 364-6799
    (416) 364-2595 (FAX)