TSX: NHK
TORONTO, Feb. 21, 2018 /PRNewswire/ - Nighthawk Gold Corp.
("Nighthawk" or the "Company") (TSX: NHK; OTCQX:
MIMZF) is pleased to announce results from the second
generation of preliminary metallurgical test work on material from
the Colomac deposit ("Colomac"), part of the Colomac Gold
Project. This second phase of testing focused on the high-grade
mineralization and showed exceptional gold recoveries of up to
98.0%.
Testing was completed at Bureau Veritas in Richmond, BC, and audited by Starkey &
Associates Inc. in Oakville,
Ontario. The current study involved mineral process test work
on one higher grade sample from Zone 1.5, while the previous study
reported on lower grade material consisting of three drill core
composite samples from various areas of the Colomac Main Sill.
Results show a relatively uniform hardness for material tested
to-date and both studies indicate that the rock is amenable to all
standard gold recovery technologies. Testwork indicated that when
using a combination of gravity recovery and cyanide leaching, gold
recoveries of up to 96.5% in the lower grade material (see press
release dated April 19, 2017), and up
to 98.0% were achieved in the higher-grade rock representing a
significant increase in recovery over the historic production
results of 88.1% (1994 to 1997). Additional test work is
being planned to further broaden investigations to include more of
Colomac's other discrete mineralized zones.
Highlights:
- Variation in rock hardness of all test samples was minimal
indicating relatively homogeneous host rock;
- Head grades varied significantly between the fire assay and
screened metallic assays due to the nugget effect of gold within
the deposit;
- Favourable recoveries were achieved for all process options,
including heap leaching, flotation, and gravity separation;
- Gold extraction by flotation ranged from 90.7% - 94.6% with
maximum tested recoveries achieved at a feed size F80 of
75 microns, optimum grade-recovery performance was not
examined;
- Cyanidation of ground rock increased gold recoveries
significantly up to 98.0%.
Dr. Michael Byron, President
& CEO commented, "Results from metallurgical testing to-date
(both the low-grade and the high-grade material), although
preliminary in nature, show the rock at Colomac to be exceptional
in terms of grind characteristics, gold recoveries, purity, and
responsiveness to all standard gold recovery technologies. We were
particularly encouraged by the preliminary heap leach bottle roll
test recoveries on the lower grade rock which showed recoveries of
81.8%. As such we have performed another bottle roll test on the
higher-grade material and a more strenuous column percolation test,
the results of which will be provided once available."
As we continue to advance the project, we will perform
additional metallurgical testing on various zones and deposits
within the Cololmac Project, including ongoing scrutiny of a
potential heap leach option for the project."
A single drill core sample from Colomac's high-grade Zone 1.5,
totalling 70 kilograms of split drill core, was submitted for
mineral process test work. As in the previous study, the higher
grade sample was 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 both studies are summarized in the tables
below. Preliminary grinding test results to-date indicate that all
four samples exhibit a consistent high hardness, and minor
variability, presenting no milling issues. The average SAG
grindability for the four samples was measured as 13.15 kWh/tonne
(Grinding from F80 6" to P80 1.7 mm) and
14.48 kWh/tonne for the Bond Ball Mill Work Index on SAG ground
rock.
Table 1. Head Assays of Colomac Samples
Sample Information
|
Fire Assay
(g Au/t)
|
Screen Metallics
Assay (g
Au/t)
|
South Zone
|
1.16
|
1.32
|
North Zone
|
0.35
|
0.90
|
Deep
|
0.65
|
1.69
|
High-Grade
|
2.83
|
7.16
|
Table 2. SAGDesign Test Summary
Sample
Information
|
SG
Solids
|
WSDT (kWh/t)
|
Sd-BWI
(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
|
Average
|
2.71
|
13.15
|
14.48
|
The high-grade sample had a head grade of 2.83 grams per tonne
gold as determined by fire assay, was 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
90.7% - 94.6% with maximum recoveries achieved at a feed size
F80 of 75 microns, while highest recoveries of 98.0%
were achieved by a combination of gravity and cyanidation.
Table 3. Master Composite Test Results
Test
|
Description
|
Particle
Size
|
Au Recovery
(%)
|
|
~P80
(microns)
|
Master
Composite
|
High
Grade
|
FLOTATION
|
Fine
|
75
|
94.9
|
94.6
|
Medium
|
106
|
94.1
|
93.5
|
Coarse
|
150
|
95.3
|
90.7
|
GRAVITY
|
Fine
|
75
|
33.3
|
54.3
|
Medium
|
106
|
45.0
|
40.5
|
Coarse
|
150
|
25.9
|
42.8
|
LEACHING
|
Whole Ore
|
150
|
96.4
|
96.4
|
Gravity +
Leach
|
106
|
96.5
|
98.0
|
Future Testing
Preliminary test work indicates that the Colomac deposit is
amenable to all standard recovery technologies, however future
studies will be broadened to include samples from other gold zones
within the mineralized sills, and to continue scrutinizing the heap
leach potential of Colomac rocks. The main purpose is to confirm
that metallurgical responses observed so far 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 a "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, the
Qualified Person as defined by NI 43-101 for this project, has
observed the collection of the samples for metallurgical testing,
reviewed the progress on the metallurgical testing on multiple
occasions and 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 17, 2013, 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 kilometres north of
Yellowknife, Northwest
Territories, Canada. Nighthawk is focused on advancing the
Colomac Gold Project with a current inferred resource of 2.1
million ounces of gold (39.8 million tonnes at an average grade of
1.64 grams per tonne), as well as advancing its other regional gold
deposits and showings within this Archean gold camp.
The Company has an experienced and dedicated team and is well
funded to complete its goals and objectives over the next 18-24
months.
The Toronto Stock Exchange has neither reviewed nor accepts
responsibility for the adequacy or accuracy of this news
release.
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 on the Colomac Gold Project, more specifically the results
of a bottle roll and column test on the higher grade sample from
Zone 1.5, 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, 2016,
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.
SOURCE Nighthawk Gold Corp.