Colibri Option Partner Announces Positive Results for Gold - Silver Bulk Sample Heap Leaching
Colibri Option Partner Announces Positive
Results for Gold - Silver Bulk Sample Heap
Leaching
Dieppe, New Brunswick--(Newsfile Corp. - August 23, 2023) - Colibri Resource Corporation (TSXV:
CBI) ("Colibri" or the "Company") is pleased to report that its option partner Tocvan Ventures (CSE:
TOC) has released results from the leaching process of
its bulk sample of material at the Pilar Gold and
Silver Project at the Pilar Project in Sonora, Mexico.
Tocvan is in year 4 of a 5-year agreement to earn an initial 51% of Colibri's Pilar Gold & Silver Project.
For full details of Colibri's agreement with Tocvan please see the Company's news release dated
September 24
th
, 2019
.
Tocvan News Release:
(August 22, 2023) - Brodie A. Sutherland, P.Geo. reports:
Highlights
Recovery Results for Heap Leaching Match Regional Operating Mines; Head Grade
Exceeds Expectations
62% Recovery of Gold Achieved Over 46-day Leaching Period
Report Confirms with Increase in Irrigation Flowrate, Higher Recovery Can Be
Achieved
Head Grade Calculated at 1.9 g/t Au and 7 g/t Ag; Extracted Grade Calculated at 1.2
g/t Au and 3 g/t Ag
Bulk Sample Only Included Coarse Fraction of Material (+3/4" to +1/8")
Fine Fraction (-1/8") Indicates Rapid Recovery with Agitated Leach
Recap of Fine Fraction and Gravity Recovery Results
Agitated Bottle Roll Test Returned Rapid and High Recovery Results:
80% Recovery of Gold and 94% Recovery of Silver after Rapid 24-hour
Retention Time
Gravity Recovery with Agitated Leach Results of Five Composite Samples Returned
95 to 99% Recovery of Gold
73 to 97% Recovery of Silver
Includes the Recovery of 99% Au and 73% Ag from Drill Core Composite at
120-meter Depth
Tocvan Ventures Corp. (the "
Company
") is pleased to provide results from a Bulk Sample completed at
its Pilar gold-silver project Sonora, Mexico. Independent Qualified Professionals at LTM of Hermosillo
have provided a final report after the completion of final analytical results. The report findings include a
base of 62% recovery of gold
and 47% recovery of silver.
Head grade
results were calculated by
LTM as
1.9 g/t Au and 7 g/t Ag
, with calculated recoverable metal extracted at 1.2 g/t Au and 3 g/t Ag.
Importantly the report notes that the first 30 days of leaching was restricted by an erratic and low flowrate
of cyanide leaching solution. This was corrected once identified through the installation of updated
irrigation systems and began instantly improving irrigation flowrate and metal recovery. LTM notes that
increased gold and silver recovery is likely with a more consistent flowrate. LTM has recommended a
duplicate column leach study of available bulk sample composite material to verify the ultimate gold and
silver extractions under heap leach. It is also important to note the low cyanide (NaCN) consumption
recorded (0.19 kg/t), indicating low cost of operation. In addition to the heap leach study, an agitated
bottle roll test was completed by LTM on a bulk sample composite for comparison of the two methods.
Rapid gold and silver recovery was recorded from minus 20 Mesh material returning
80% recovery of
gold and 94% recovery of silver after just 24-hours of retention time
. Follow-on agitated leach and
gravity tests are recommended to further evaluate the ability to utilize rapid recovery methods in lieu of
the slower heap leach method. The Company is extremely pleased with the analytical results and insights
gained through the bulk sample process which will guide future development and provide added
confidence in the optimal extraction method.
"The Bulk Sample process has been extremely important to the understanding of the surface
expression of mineralization at Pilar along with defining a path towards optimal gold and silver
recovery."
Stated Brodie Sutherland, CEO.
"We are encouraged by the strong heap leach
results for gold where the data suggests recovery can be improved through increased leaching
solution flowrate over a consistent and longer leaching period. Perhaps the most encouraging
development from the study is the characterization of exposed gold and silver amenable to rapid
gravity and agitated leach recovery. A quicker turnaround for metal extraction at very high
recovery rates adds a new positive factor to the development path of the relatively high-grade
nature of Pilar. Having optionality to explore both methods as viable extraction techniques
makes Pilar a unique and standout deposit for the region and with the potential now to explore
an even greater area around to add to the potential resource size makes us even more excited
for the future of the project."
Figure 1.
Heap Leach Bulk Composite Sample. Flowrate versus time and Cumulative Gold and
Silver Extraction versus time. Irrigation flowrate was improved after day 30 of the test having a positive
impact on metal recovery.
To view an enhanced version of this graphic, please visit:
https://images.newsfilecorp.com/files/4269/178234_949ba4d344b9d88c_001full.jpg
LTM Conclusions and Recommendations
1
.
A cyanide agitated bottle roll test conducted on the Bulk Composite Sample at a grind size of
100% minus 20 Mesh (850 microns) showed high gold and silver extractions of approximately
81% and 99% respectively after a retention time of 72 hours. It is important to point out that fast
gold and silver dissolution kinetics were obtained and gold and silver extractions of 80% and
94% respectively were achieved after 24 hours of retention time.
2
.
It is recommended to conduct a cyanide agitated bottle roll study on the Bulk Composite
Sample at three grind sizes of P80 of 100 Mesh (150 µm), 140 Mesh (106 µm) and 200 Mesh
(75 µm) to evaluate the impact of grind size upon gold and silver extraction.
3
.
The cyanide pilot heap test conducted on the Bulk Composite Sample at a crush sizes of
+3/4"+1/8" showed gold and silver extractions of 61.84% and 47.27% respectively after a leach
cycle of 46 days. Problems in the solution pumping system during the first 30 days of leach
cycle affected the gold and silver extractions during the first 30 days of leach cycle. Therefore, it
is recommended to conduct a duplicate column tests on the Bulk Composite Sample at a crush
sizes of +3/4"+1/8" for determining the ultimate gold and silver extractions under heap leach
type of leaching regime.
4
.
It is recommended to conduct additional metallurgical test work on the Bulk Composite Sample
at a crush size of 100% -1/8" which will provide additional information on the overall gold and
silver recoveries and potential process options for processing the mineral resources from the El
Pilar Gold Project. The following paragraphs summarize the recommended testwork and the
objectives:
1
.
A)
Two cyanide locked cycle column tests (1 Test with Agglomeration with Portland Cement 1
Test Without Agglomeration) to evaluate if it is feasible to leach the fine fraction (100% -1/8") of
the Bulk Composite Sample without presenting percolation problems.
2
.
B)
Gravity Concentration at a grind of 80% minus 150 µm using a Knelson Laboratory
Concentrator. The objective of the test will be to evaluate the amenability of recovery the free
gold contained in the fine fraction of the Bulk Composite Sample.
3
.
C)
Gravity Concentration at a grind of 80% minus 150 µm using a Wilfley Concentrator Table.
The objective will be to evaluate the amenability of recovery potential free gold contained in the
fine fraction of the Bulk Composite Sample using the Wilfley Concentrator Table.
Figure 2.
Cyanide Agitated Bottle Roll Test from Bulk Composite Sample. Rapid recovery of gold
(80%) and silver (94%) achieved after 24-hours of retention time.
To view an enhanced version of this graphic, please visit:
https://images.newsfilecorp.com/files/4269/178234_949ba4d344b9d88c_002full.jpg
Diagnostic Leach Study Summary
Full results from the Diagnostic Leach Study are available on the Company's website and in the March
29
th
news release. A summary is provided below to further demonstrate the potential to utilize rapid
recovery methods.
Table 1.
Summary of Results from the Precious Metals Diagnostic Leach Study completed by LTM.
Sample
ID
Location
Head Screen
Assay
Gravity Concentrate
Assay
Total Recoverable by Gravity and
Agitated Cyanide Leach
Au (g/t)
Ag (g/t)
Au (g/t)
Ag (g/t)
Au (%)
Ag (%)
494741
Main Zone
(Surface)
6.2
23
76.2
237
95
78
494743
Main Zone
(Surface)
8.2
68
117.0
1152
98
97
494745
Main Zone
(Surface)
2.7
9
35.6
82
97
90
494747
4-T (Surface)
20.4
74
290.3
568
98
85
494749
Main Zone (Drill
Core)
24.9
9
231.1
53
99
73
About the Pilar Property
The Pilar Gold-Silver property has recently returned some of the regions best drill results. Coupled with
encouraging gold and silver recovery results from metallurgical test work, Pilar is primed to be a
potential near-term producer. Pilar is interpreted as a structurally controlled low-sulphidation epithermal
system hosted in andesite rocks. Three primary zones of mineralization have been identified in the north-
west part of the property from historic surface work and drilling and are referred to as the Main Zone,
North Hill and 4-T. The Main Zone and 4-T trends are open to the southeast and new parallel zones have
been recently discovered. Structural features and zones of mineralization within the structures follow an
overall NW-SE trend of mineralization. Mineralization extends along a 1.2-km trend, only half of that trend
has been drill tested so far. To date, over 23,000 m of drilling has been completed.
2022 Phase III Diamond Drilling Highlights include (
all lengths are drilled thicknesses
):
116.9m @ 1.2 g/t Au, including 10.2m @ 12 g/t Au and 23 g/t Ag
108.9m @ 0.8 g/t Au, including 9.4m @ 7.6 g/t Au and 5 g/t Ag
63.4m @ 0.6 g/t Au and 11 g/t Ag, including 29.9m @ 0.9 g/t Au and 18 g/t Ag
2021 Phase II RC Drilling Highlights include (
all lengths are drilled thicknesses
):
39.7m @ 1.0 g/t Au, including 1.5m @ 14.6 g/t Au
47.7m @ 0.7 g/t Au including 3m @ 5.6 g/t Au and 22 g/t Ag
29m @ 0.7 g/t Au
35.1m @ 0.7 g/t Au
2020 Phase I RC Drilling Highlights include (
all lengths are drilled thicknesses
94.6m @ 1.6 g/t Au, including 9.2m @ 10.8 g/t Au and 38 g/t Ag;
41.2m @ 1.1 g/t Au, including 3.1m @ 6.0 g/t Au and 12 g/t Ag ;
24.4m @ 2.5 g/t Au and 73 g/t Ag, including 1.5m @ 33.4 g/t Au and 1,090 g/t Ag
15,000m of Historic Core RC drilling. Highlights include:
61.0m @ 0.8 g/t Au
16.5m @ 53.5 g/t Au and 53 g/t Ag
13.0m @ 9.6 g/t Au
9.0m @ 10.2 g/t Au and 46 g/t Ag
Brodie A. Sutherland, P.Geo., CEO for Tocvan Ventures Corp. and a qualified person ("
QP
") as defined
by Canadian National Instrument 43-101, has reviewed and approved the technical information
contained in this release.
Quality Assurance / Quality Control
Oversight and management of the Bulk Sample was completed by an independent group of qualified
professionals at LTM (Laboratorio Tecnológico de Metalurgia) of Hermosillo. As part of the Company's
robust QA/QC procedures, duplicate samples of cyanide solutions are submitted to LTM in Hermosillo,
Sonora. LTM facilities are an ISO 17025 and ISO 9001:2015 certified lab. A second duplicate of
cyanide solutions are submitted to SGS in Durango. Gold and silver are analyzed using 30g nominal
weight fire assay with AA finish for Au and gravimetric determination for Ag. Other elements are
analyzed using aqua regia digestion with an ICP finish.
ABOUT COLIBRI RESOURCE CORPORATION:
Colibri is a Canadian-based mineral exploration company listed on the TSX-V (CBI) and is focused on
acquiring and exploring prospective gold & silver properties in Mexico. The Company holds six highly
prospective precious metal properties, all of which have planned exploration programs for calendar
2023.
For more information about all Company projects please visit:
www.colibriresource.com
.
Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in
the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy
of this release.
Notice Regarding Forward-Looking Statements:
This news release contains "forward-looking statements." Statements in this press release which are not
purely historical are forward-looking statements and include any statements regarding beliefs, plans,
expectations or intentions regarding the future. Actual results could differ from those projected in any
forward-looking statements due to numerous factors. These forward-looking statements are made as of
the date of this news release, and the Company assumes no obligation to update the forward-looking
statements, or to update the reasons why actual results could differ from those projected in the forward-
looking statements. Although the Company believes that the plans, expectations and intentions
contained in this press release are reasonable, there can be no assurance that they will prove to be
accurate.
For information contact: Ronald J. Goguen, President, Chairperson and Director, Tel: (506) 383-4274,
.
To view the source version of this press release, please visit
https://www.newsfilecorp.com/release/178234