La Negra silver discovery was made in the fall of 2014 and is one of
several new prospects recently identified within a 25 x 15 km
mineralized corridor, referred to as the 'Promontorio Mineral Belt'
- La Negra is optioned to Pan American Silver Corp., which includes the Promontorio Silver Resource, located 7 kilometres south of La Negra, also part of the Promontorio Mineral Belt
- Pan American Silver can earn 75% interest by spending US$16M on expenditures and
payments within a four-year period with Kootenay retaining a 25%
carried to production interest
date, 70 drill holes have been completed by Kootenay and Pan American Silver with most returning high
grade, wide spread silver mineralization from surface to a vertical
depth of over 300 metres; click
the following link to view the comprehensive results of all the
drill holes completed to date:
La Negra Drill Results
The initial 25 drill holes in
the discovery program averaged 107 g/t silver in the breccia, with
continuous mineralization with widths of up to 200 metres and
averaged 150g/t silver in the breccia using a 75 g/t cutoff.
Drill hole LN 21 has been the
best hole to date with 156 g/t silver over 200 metres including the
bottom 50 metres with 420 g/t and 6 metres of 1337 g/t silver.
Potential for an attractive open
pit scenario is supported by a
prominent hill top formed by mineralization and good silver grades.
Mineralization is hosted in a diatreme breccia, which also indicates
a depth potential of several hundreds of metres.
Ongoing ground exploration
within a 2-3 kilometre radius of the La Negra Breccia has identified
two high priority mineralized trends with clear underlying geologic
controls. These have been named the 'La Negra silver trend' and
'Vania'. Additional areas of silver and gold mineralization
identified apart from these trends are currently being evaluated.
La Negra has been compared to
Pan American's Alamo
Dorado Mine located 190 kilometres to the south. Alamo Dorado's
mineral zone formed a prominent hill that is now a low strip open
pit. - La Negra mineral zone also forms a prominent hill; lending
itself to the potential of a low strip open pit mining situation.
La Negra silver discovery is situated only 7 kilometres north of
the Promontorio Silver Resource within the Promontorio Mineral Belt,
in the state of Sonora, Mexico. The
Promontorio Mineral Belt is currently under option to Pan American
Silver whereby it can earn a 75% interest in the project by spending
US$16 million on expenditures and payments with Kootenay retaining a
25% carried to production interest. To
date, Kootenay has completed two successful drill programs totaling
41 drill holes on the La Negra silver discovery with most drill holes
returning significant and consistent intervals of high grade,
widespread silver mineralization extending from surface to depth of
300 metres. To date, 17,000 metres over 87 holes have been drilled confirming high-grade as well as the presence of a second breccia zone further to the south, which currently remains open at depth. Pan American is currently mapping and sampling to define additional targets in the area.
Ongoing exploration by Kootenay’s technical team in 2014, resulted
in the discovery of La Negra Breccia. Initial exploration on the La Negra prospect
geophysics, petrographic analysis, trenching and surface sampling. These programs validated extensive silver mineralization over a
large surface area measuring approximately 100 to 200 metres in width
by 500 metres in length. To follow up the initial exploration
programs, Kootenay completed a Phase I drill program on La Negra,
which returned significant and consistent intervals of high grade,
widespread silver mineralization extending from surface to depth,
confirming a substantial new silver discovery. In 2015, Kootenay
carried out a Phase II drill program that further confirmed the
continuity of silver grades and the consistency of silver
mineralization to depth within the core of the diatreme breccia.
These results further reinforced La Negra's future as a potential
low-cost, open pittable silver resource, which ultimately led to Pan America Silver's interest in the project.
Pan American Silver began managing the exploration program in April 2016 and commenced re-logging drill core, geological mapping and re-interpretation, and completed 62 km of magnetic ground surveys. A 3,500-meter drilling program was initiated by Pan American Silver in July 2016 with the objective of infilling the Kootenay operated La Negra drill program with coverage to 50 meter centres and testing the along-strike and down dip extents, as well as following up on geophysical and geological anomalies located elsewhere within the Promontorio concessions. Pan American Silver reported that a series of deeper infill drill holes from the first 12 holes of the 2016 program confirming high-grade results from previous drilling conducted by Kootenay on La Negra (See Kootenay News release October 25, 2016). Drill results also confirmed the presence of a second breccia zone further to the south, which currently remains open at depth. Based on these successes, Pan American Silver extended the 2016 drill program by approximately 2,000 meters, which was also successful in intercepting consistent high-grade silver mineralization at depth (See Kootenay News release February 15, 2017). To date, Pan American Silver has completed a total of 46 holes totalling over 11,000 metres of drilling on the La Negra Breccia. Click the following link to view the La Negra Drill Results.
date, results from preliminary metallurgical testing of La Negra show
potential for high silver recoveries by both leach extraction and
flotation methods. Silver extraction in seven bottle roll
tests (leach tests) ranged from 71 to 90%. Silver extraction in
three rougher flotation tests ranged from 85 to 98%. Importantly,
silver extraction by leaching was not influenced by sulphide sulphur
content, and a sample of material from 100 to 200 metres below
surface had 89% extraction in a bottle roll test. High silver
recoveries by leaching, including in sulphide material, indicate
potential for silver to be recovered on site in a dore, substantially
reducing costs and discounts associated with a sulphide concentrate
produced by flotation.
test work was completed by Kappes Cassiday and Associates of Reno,
Nevada, under the direction of Hans Smit, P.Geo, a Qualified Person
as defined by NI 43-101. Seven samples were created for testing
comprised of material from 9 or 10 sub-samples of drill core rejects
from across the area drilled and grouped by specific vertical depth
and grade ranges. Bottle roll leach tests were conducted on a
1,000 gram portion of each sample that was ring and puck pulverized
to a target size of 80% passing 0.075 millimetres. Tests were
run for a total of 96 hours, but in most tests the majority of the
silver was recovered in the first 2 to 4 hours. Cyanide and
lime inputs were not optimized.