Minefinders' Delores silver grades increased
Minefinders Corporation Ltd MFL
Shares issued 16,300,709 Jun 6 close $1.19
Thu 7 Jun 2001
Mr. Mark Bailey reports
Continuing metallurgical and geochemical tests indicate that silver grades
and resource in the Dolores deposit, located in Chihuahua, Mexico, are
significantly greater than previously estimated. These new data are based
upon multiacid (total) digestion ore-grade analyses of 307 mineralized
drill samples by ALS-Chemex Labs in Vancouver. The economic impact of
increased silver content and grade is expected to be substantial, as in-pit
resources are effectively moved from waste to ore categories resulting in
reduced strip ratios, additional silver production and accelerated cash
flow. The previously reported resource for the company's 100-per-cent-owned
Dolores project was 2.45 million ounces of gold and 129.7 million ounces of
silver (see news in Stockwatch Sept. 18, 2000).
The company was originally alerted to the possibility of underreporting of
silver values at Dolores when column-leach tests (by McClelland Labs)
indicated that ores contained an average 30 per cent more silver than that
predicted from the original geochemical analysis of drill material. A check
analysis of 307 five-foot samples from 12 drill holes representing
different portions of the deposit showed significant increases in overall
silver assay grades when total digestion techniques were used. These
results confirm that silver has been underreported for the deposit. Of the
307 samples, 52 samples were reassayed as check samples and results for 21
high-grade samples compared favourably to previous fire assays. Check
assays were used to assure high levels of quality control and confidence in
these new results.
Comparison of aqua-regia digestion and multiacid digestion assay results
for low- to mid-grade silver mineralization at Dolores (up to 100 grams per
tonne) are presented in Table 1 below. In addition, total digestion results
compare favourably with high-grade (more than 100 g/t) fire assay
quantitative results.
Table 1
Type of mineralization: Oxide
No. of samples: 119
Average grade Ag multiacid (g/t): 38.8
Average grade Ag aqua regia (g/t): 26.0
Per cent change: plus 49.4%
Per cent of resource: 33.1%
Type of mineralization: Mixed
No. of samples: 105
Average grade Ag multiacid (g/t): 28.7
Average grade Ag aqua regia (g/t): 24.5
Per cent change: plus 16.8%
Per cent of resource: 42.7%
Type of mineralization: Sulphide
No. of samples: 62
Average grade Ag multiacid (g/t): 34.2
Average grade Ag aqua regia (g/t): 33.6
Per cent change: plus 1.7%
Per cent of resource: 24.2%
Type of mineralization: High-grade
No. of samples: 21
Average grade Ag multiacid (g/t): 188.75
Average grade fire assay: 186.29
Per cent change: 1.3%
The company consulted in detail with both ALS-Chemex quality assurance
professionals and Bondar-Clegg Laboratories personnel in comparing the two
analytical techniques. The industry standard, aqua-regia digestion with
atomic absorption (AA) analysis, used for all previous Dolores samples, is
considered a partial digestion, in laboratory terms. As reported by Steve
Armstrong, manager of Bondar-Clegg Laboratories in Hermosillo, Sonora,
Mexico: "There are some areas, especially in Mexico, where the silver
content is significantly higher in total digestion assays because partial
digestion by aqua-regia results in reporting lower grades of silver
mineralization. This results in subsequent lower estimation of mineral
resources, due to silver results that do not reflect true total content."
At Dolores incomplete silver dissolution in aqua regia is believed to be
due primarily to the presence of silver halide minerals that occur in
substantial quantity within both oxidized and mixed oxide-sulphide material
in the Dolores resource.
Recovery rates and percentage recoveries predicted by column leach tests
were based upon total digestion analysis procedures and will not be
affected by this new information. Total recovered silver from the deposit
will reflect the increased silver grades and content of the deposit.
An extensive check assay program was followed by ALS-Chemex to confirm the
new assay numbers. A total of 52 samples including several complete sample
intervals were check assayed by ALS-Chemex to verify the new data. All
samples from the intercepts have been stored in the ALS-Chemex storage
facility in Chihuahua, Mexico, since the 2000 drill program and original
pulps were retrieved by ALS-Chemex for reanalysis.
The projected impact of higher silver grades in the Dolores deposit is an
increase in silver production, lower strip ratios, reduced production cost
per ounce and accelerated cash flows.
Additional total digestion assays will be completed on mineralized drill
intercepts from the Dolores deposit and results from these new silver
grades incorporated into the block model. Comparison studies on the
company's other projects in Mexico are also being conducted to provide
accurate assay data for silver. All gold assays from Dolores were done
using fire assay techniques and therefore are not impacted by aqua-regia
digestion.
Quality assurance professionals from Chemex and Bondar-Clegg and
Minefinders management are qualified persons as defined by CSA/NI 43-101.
WARNING: The company relies upon litigation protection for
"forward-looking" statements.
(c) Copyright 2001 Canjex Publishing Ltd. stockwatch.com |
