VANCOUVER, BRITISH COLUMBIA--Pacific Rim Mining Corp. is pleased to announce
it has received the results from bottle roll tests conducted in the initial phase of metallurgical testing of mineralized rock from its
Luicho gold project located in southern Peru, and the results from 1,033 new surface rock chip channel samples.
Bottle roll tests
Pacific Rim has identified two types of metallurgically distinct rock at Luicho; carbonaceous and noncarbonaceous. Where
present, the carbonaceous mineralization is confined to the uppermost 10 meters of the 400-plus meter thick sandstone unit and
likely resulted from the mobilization of carbon from the overlying shale unit.
Three bulk samples of 1 to 2 g/t gold, noncarbonaceous mineralized material were collected in March, 2000 from underground
workings. Four bottle roll tests (representing crush sizes of minus 2``, minus 1', minus 1/2`` and minus 5 mesh (approximately
3/16') were conducted per bulk sample. These tests returned gold recoveries of: 94%, 89% and 87% for the minus 5 mesh
material; 90%, 84% and 93% for the minus 1/2`` material; 91%, 73% and 68% for the minus 1' material; and 89%, 71% and
68% for the minus 2`` material. This confirms petrographic studies that indicate gold at Luicho occurs as free gold in open
spaces and fracture fillings. Cyanide and lime reagent consumption was low to moderate.
For the much less common carbonaceous mineralization, two bulk samples were collected and tested at four crush sizes.
Recoveries vary in this material from 19% to 61%. However, bottle roll tests are typically not accurate tests for determining
ultimate gold recovery when using carbonaceous materials (since the gold grades in solution are extremely high in comparison to
field conditions and the effect of the carbon is accentuated). Column leach tests are expected to significantly improve these
recoveries.
Noncarbonaceous rock constitutes 94% and carbonaceous rock represents a maximum of 6% of the 175 meters of vertical
stratigraphic dimension over which mineralization at Luicho has been documented to date.
Surface and cliff sampling
An additional 1,033 two-meter long continuous rock chip channel samples have been collected from the Luicho target, bringing
the total number of samples collected to date to 6,535. The average grade of all 6,535 samples is 1.52 g/t gold. These samples
represent a total of 194 channels (composed of two or more individual 2 meter long samples strung together end to end) in and
around the Structural Corridor, as well as numerous individual samples. The Structural Corridor is a 1.85 kilometre long by 250
meter wide zone of intense fracturing that Pacific Rim believes is the core of the Luicho target. It has been subdivided into 3
zones based on the degree of fracturing. The cumulative results of Pacific Rim's sampling to date in each of the 3 zones that
comprise the Structural Corridor are summarized in the table below.
Zone # of samples average grade of % of samples average grade
in total total samples exceeding 0.31 of samples
g/t gold cutoff exceeding 0.31
g/t gold cutoff
Northeast 1100 1.33 g/t gold 69% 1.87 g/t gold
Central 2195 3.04 g/t gold 69% 4.37 g/t gold
South 636 1.30 g/t gold 52% 2.37 g/t gold
Total for
structural
corridor 3932 2.28 g/t gold 66% 3.39 g/t gold
Ninety-seven of the new samples (represented by 11 channels) were collected from cliff faces. These samples were taken
primarily from the Northeast Zone and cover vertical dimensions ranging from 11 to 25 meters. Assay results from these
samples confirm the continuity of grade in a vertical dimension and mimic, with local variation, the results of adjacent surface
samples. Vertical sampling results include: 4.15 g/t gold over 21 meters vertically; 1.40 g/t gold over 21 meters; 2.58 g/t gold
over 17 meters; and, 0.81 g/t gold over 25 meters.
Tom Shrake, CEO states ``The results we obtained from the bottle roll tests have greatly exceeded our expectations and clearly
indicate that Luicho mineralization will be heap leachable with excellent recoveries. Given the unusually high recoveries for the
minus 2' material, we are very optimistic that heap leaching of uncrushed materials is possible. These results should allow the
cut-off grade to be reduced, which in turn provides additional ounces by adding lower grade materials for processing that would
otherwise have been considered waste. The bottom line is capital savings and reduced operating costs for a potential operation.
The cliff samples are like having short drill holes, and these results provide comfort that the mineralization has continuity in the
vertical dimension. Cliff sampling will continue over the coming weeks. The geological mapping is largely completed and is in the
process of being compiled. The mapping continues to indicate the importance of moderate to high angle faulting as the main
control to mineralization. From this mapping we take comfort that Luicho has excellent potential in the vertical dimension. We
will begin column tests on four of the bulk samples as soon as possible. These tests will be conducted at the minus 1`` and minus
1/2 ' crush size. In addition, a site will be sought for a 1/2-tonne low grade sample for the purpose of conducting run-of-mine
(uncrushed) leach tests. We are also working to characterize the carbonaceous materials, which we expect will ultimately
provide average gold recoveries. As planned, we are aiming to take as much risk out of the Luicho project as we can, and we
just took two giant strides in that direction.``
Pacific Rim's access road to the property is progressing on schedule and should reach the site shortly, after which drill pad
construction will commence. This is in preparation for a minimum 12,000 meter first phase drill program, expected to get
underway in the spring of 2000.
Sampling is supervised by Pacific Rim's geologists David Ernst and Peter Dilles and the Luicho program is ultimately supervised
by Thomas Shrake, CEO of the Company. Samples are assayed by Bondar Clegg, an ISO9002-registered analytical
laboratory in Vancouver, BC, after first being prepared at their facility in Lima. A check assay program is on-going with
Chemex Labs. Metallurgical test work is being conducted at McLelland Labs in Reno, NV, under the supervision of G.
McLelland.
Please visit Pacific Rim's website (www.pacrim-mining.com) for a map of the latest sampling results, which, alternatively, is
available from the Company by fax.
On behalf of the board of directors,
Thomas C. Shrake, CEO
This news release contains forward-looking statements regarding upcoming programs and expected results. Actual results may
differ materially from those currently anticipated in such statements. |
