TORONTO, March 19, 2019 /PRNewswire/ - Nighthawk
Gold Corp. ("Nighthawk" or the "Company") (TSX: NHK; OTCQX:
MIMZF) is pleased to provide results from the latest
metallurgical testwork on the Colomac Gold Project
("Colomac"). Four bulk drill core samples were collected
from 21 boreholes covering 7 mineralized zones within the Colomac
and Goldcrest sills. The results are presented in Table 3 and
include a summary of test results from all three preliminary
metallurgical studies now completed. Findings continue to reveal: a
relatively uniform hardness for material tested to-date; that the
rock is amenable to all standard gold recovery technologies; and
using a combination of gravity and cyanide leach recovery
processes, testing showed that gold recoveries for all six bulk
samples tested to-date range from 96.3% on the lower-grade material
up to 98.0% for the higher-grade material, representing a
significant increase in recovery over historic production results
of 88.1% (1994 to 1997).
Dr. Michael Byron, President & CEO commented, "So far
we have tested six samples that cover a limited portion of the
deposit, however we are extremely encouraged as we continue to see
tremendous consistency in terms of grind characteristics, gold
recoveries, and responsiveness to all standard gold recovery
technologies. The current program was intended to broaden
sampling both laterally, and to depth, and to test material from
several other mineralized zones. The results have been exceptional
and show a very strong consistency in physical characteristics
throughout the seven zones tested to-date. We will continue to
expand metallurgical testwork in 2019 to additional areas of
the sills, including more bottle roll and column leach
tests to address the potential heap leach option for
Colomac."
Testwork Highlights:
- A total of six bulk drill core samples spanning 3 metallurgical
studies have now been collected from 7 mineralized zones within the
Colomac and Goldcrest sills;
- Minimal variation in rock hardness is noted for all test
samples indicating a relatively homogeneous host rock across both
sills;
- Favourable recoveries were achieved for flotation, gravity
separation, and leaching;
- Gold extraction by flotation ranged from 90.7% - 98.1% with
maximum tested recoveries achieved at a feed size
F80 of 75 microns (optimum grade-recovery
performance was not examined);
- Cyanidation of ground rock after gravity concentration
increased gold recoveries across the board up to 98.0%;
- Results to-date compare favourably to similar
North America projects.
Cyanide bottle roll and column percolation metallurgical testing
on half inch crushed material from the four samples is nearing
completion and results will be provided once available. The Company
will then have completed 6 bottle roll and 5 column leach tests
offering valuable insight into the ongoing assessment of the
deposit's heap leach potential. Additional metallurgical work will
be expanded to include more mineralized zones and to address
potential grade variations within the Colomac and Goldcrest sills.
As in the previous sampling programs, testwork will be carried out
on Colomac drill core from the most recent drilling.
Metallurgical Testwork and Samples
Testing was completed at Bureau Veritas in Richmond, BC,
and audited by Starkey & Associates Inc. in Oakville,
Ontario. Studies completed to-date have involved the current
drill core mineral process testwork on four composite samples, one
higher grade sample from Zone 1.5 (see press releases dated
February 21, 2018 and May 22, 2018), and on lower-grade material
consisting of three composite samples from various areas of the
Colomac Main Sill (see press release dated April 19, 2017). Locations of the drillholes
sampled for each of the metallurgical studies are shown in Figure
1.
In 2016, three drill core bulk samples of similar mineralogical
characteristics totalling 119.5 kg of lower-grade mineralization
were collected from different regions (Zone 1.5 composite labeled
as North Zone, Zone 3.0 and 3.5 labeled as South Zone, and Deep
constituted various areas of the sill at depth) and elevations in
the deposit to facilitate hardness testing (Table 1), and to
address spatial and grade variations of the quartz diorite host
rock (Table 2). Grinding test results indicate that all samples
exhibit a consistent high hardness and show minor variability, thus
they would present no milling issues (see press release dated
April 19, 2017). A single master
composite sample was then blended for the metallurgical testwork.
Recoveries are summarized in Table 3.
In 2017, a 70 kg sample of split drill core was collected from
Colomac's High-Grade Zone 1.5, (Table 1) and submitted for
identical mineral process testwork as was conducted on the
lower-grade material, to examine the impact of grade on process
metallurgy. Results showed an increase in recoveries over the
lower-grade material from 96.4% to 98.0% (see press releases dated
February 21, 2018 and May 22, 2018).
The most recent campaign broadened sampling to other areas of
the deposit including Zones 1.0, 2.0/2.5, 3.0/3.5 and Goldcrest
North (Table 1). The testwork program was identical to the previous
two campaigns, with each sample composed of approximately 70 kg of
drill core collected from the respective zones. As in the previous
studies, samples were assayed for gold (Table 1), tested for
grindability using the SAGDesign methodology (Table 2) and for
amenability to several gold recovery processes (Table 3). For
comparison, results from all three generation of studies are
summarized in the tables. Preliminary grinding test results for the
current study show that all four samples exhibit a consistent high
hardness, with minor variability, thus mitigating milling issues.
The average SAG grindability for the four samples was measured as
13.29 kWh/tonne (Grinding from F80 6" to P80
1.7 mm) and 14.78 kWh/tonne for the Bond Ball Mill Work Index
(closed with a 150 micron screen) on SAG ground rock, remarkably
consistent with previous test results.
Results from all studies to-date are summarized in the tables
below and show that preliminary grinding testwork characterizes all
samples as having a consistent high hardness with minor
variability, and that the material tested responds favourably to
the proposed process options.
Table 1. Head Assays of three generations of Colomac Samples
Sample
Information
|
Fire Assay
(gpt Au)
|
Screen
Metallics
Assay (gpt Au)
|
Sample
Generation
|
News
Release
|
South Zone
|
1.16
|
1.32
|
2016
|
April 19,
2017
|
North Zone
|
0.35
|
0.9
|
Deep
|
0.65
|
1.69
|
High-Grade
|
2.83
|
7.16
|
2017
|
February 21, 2018;
May 22, 2018
|
Zone 1.0
|
1.67
|
2.28
|
2018
|
current
release
|
Zone
2.0-2.5
|
2.15
|
2.05
|
Zone
3.0-3.5
|
2.38
|
2.41
|
Goldcrest
North
|
1.34
|
2.29
|
Table 2. SAGDesign Test Summary
|
|
|
|
Sample
Information
|
SG
Solids
|
WSDT
|
Sd-BWI
|
(kWh/t)
|
(kWh/t)
|
*South
Zone
|
2.76
|
12.32
|
14.28
|
*North
Zone
|
2.73
|
13.52
|
14.38
|
*Deep
|
2.70
|
14.07
|
14.10
|
High-Grade
|
2.67
|
12.69
|
15.18
|
Zone 1.0
|
2.7
|
13.49
|
15.43
|
Zone
2.0-2.5
|
2.62
|
11.74
|
14.93
|
Zone
3.0-3.5
|
2.71
|
11.48
|
13.90
|
Goldcrest
North
|
2.61
|
16.45
|
14.88
|
Average
|
2.69
|
13.22
|
14.64
|
*Blended into a
"Master Composite" as seen in Table 3
|
The four sample head grades varied from 1.34 gpt Au to 2.38 gpt
Au as determined by fire assay, and were tested for gold recovery
amenability, specifically by cyanide leaching, flotation, and
gravity separation. Favourable recoveries were achieved for all
process options. Gold recoveries by flotation ranged from 84.8% -
98.1% with maximum recoveries achieved at a feed size
F80 of 75 microns, for Goldcrest North material.
Table 3. Metallurgical Test Results
Test
|
Description
|
Particle
Size ~P80
(microns)
|
Au Recovery
(%)
|
Sample
Generation
|
2016
|
2017
|
2018
|
Master
Comp.
|
High
Grade
|
Zone
1.0
|
Zone
2.0-2.5
|
Zone
3.0-3.5
|
Goldcrest
North
|
Flotation
|
Fine
|
75
|
94.9
|
94.6
|
94.9
|
94.8
|
92.1
|
98.1
|
Medium
|
106
|
94.1
|
93.5
|
94.5
|
94.5
|
88.6
|
94.9
|
Coarse
|
150
|
95.5
|
90.7
|
92.8
|
94.2
|
84.8
|
95.5
|
Gravity
|
Fine
|
75
|
33.3
|
54.3
|
53.0
|
42.0
|
27.2
|
58.3
|
Medium
|
106
|
45.0
|
40.5
|
48.2
|
58.8
|
24.5
|
44.4
|
Coarse
|
150
|
25.9
|
42.8
|
34.4
|
34.1
|
20.4
|
52.0
|
Ground
Leach
|
Whole Ore
|
150
|
96.5
|
96.4
|
97.1
|
96.8
|
96.7
|
97.2
|
Gravity +
Leach
|
106
|
96.4
|
98.0
|
98.0
|
97.3
|
96.3
|
96.8
|
Future Testing
Preliminary testwork indicates that the Colomac deposit is
amenable to all standard recovery technologies, however future
studies will be broadened to include samples from other satellite
gold zones and other zones to depth within the mineralized sills.
Future work will also continue scrutinizing the heap leach
potential of the Colomac deposit. The main objective is to confirm
that the metallurgical responses observed so far will apply over a
broader range of head grades and zone locations.
Quality Control and Qualified Persons
The technical information disclosed herein was prepared under
the supervision of Dr. Alice Shi of Bureau Veritas and
Mr. John Starkey of Starkey & Associates Inc., who is
considered an independent "Qualified Person" as defined by NI
43-101 for the metallurgical testing performed on behalf of
Nighthawk Gold Corp. Mr. Starkey has supervised the metallurgical
work reported on and has reviewed and approved the technical
disclosure contained in this news release with respect to such
work.
Dr. Michael J. Byron, Ph.D.,
P.Geo., President & Chief Executive Officer of Nighthawk, who
is the "Qualified Person" as defined by NI 43-101 for this project,
has reviewed and approved of the technical disclosure contained in
this news release. Please refer to NI 43-101 technical report
"Technical Report and mineral resource estimate update on the
Colomac Property of the Indin Lake Project", dated June 13, 2018, as filed under the company's
profile on www.sedar.com
About Nighthawk
Nighthawk is a Canadian-based gold exploration company with 100%
ownership of a district-scale land position within the Indin Lake
Greenstone Belt, located approximately 200 km north of Yellowknife, Northwest Territories, Canada.
Nighthawk is focused on advancing the Colomac Gold Project with a
current inferred resource of 2.6 million ounces of gold (50.3
million tonnes at an average grade of 1.62 grams per tonne gold),
as well as advancing its other regional gold deposits and showings
within this largely underexplored Archean gold camp.
The Company has an experienced and dedicated team and is well
funded to complete its goals and objectives over the next 12-18
months.
Forward-Looking Information
This news release contains "forward-looking information" within
the meaning of applicable Canadian securities legislation.
Forward-looking information includes, but is not limited to,
information with respect to the Company's continued metallurgical
testing at Colomac and the timing and results thereof. Generally,
forward-looking information can be identified by the use of
forward-looking terminology such as "plans", "expects", or "does
not expect", "is expected", "budget", "scheduled", "estimates",
"forecasts", "intends", "anticipates", or "does not anticipate", or
"believes" or variations of such words and phrases or state that
certain actions, events or results "may", "could", "would",
"might", or "will be taken", "occur", or "be achieved".
Forward-looking information is based on the opinions and
estimates of management at the date the information is made, and is
based on a number of assumptions and is subject to known and
unknown risks, uncertainties and other factors that may cause the
actual results, level of activity, performance or achievements of
Nighthawk to be materially different from those expressed or
implied by such forward-looking information, including risks
associated with the exploration, development and mining such as
economic factors as they effect exploration, future commodity
prices, changes in foreign exchange and interest rates, actual
results of current exploration activities, government regulation,
political or economic developments, environmental risks, permitting
timelines, capital expenditures, operating or technical
difficulties in connection with development activities, employee
relations, the speculative nature of gold exploration and
development, including the risks of diminishing quantities of
grades of reserves, contests over title to properties, and changes
in project parameters as plans continue to be refined as well as
those risk factors discussed in Nighthawk's annual information form
for the year ended December 31, 2017,
available on www.sedar.com. Although Nighthawk has attempted to
identify important factors that could cause actual results to
differ materially from those contained in forward-looking
information, there may be other factors that cause results not to
be as anticipated, estimated or intended. There can be no assurance
that such information will prove to be accurate, as actual results
and future events could differ materially from those anticipated in
such information. Accordingly, readers should not place undue
reliance on forward-looking information. Nighthawk does not
undertake to update any forward-looking information, except in
accordance with applicable securities laws.
Neither the Toronto Stock Exchange has neither reviewed nor
accepts responsibility for the adequacy or accuracy of this news
release.
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SOURCE Nighthawk Gold Corp.