TSX: NHK
TORONTO, May 22, 2018 /CNW/ - Nighthawk Gold Corp.
("Nighthawk" or the "Company") (TSX: NHK; OTCQX:
MIMZF) is pleased to provide a summary of results from its
ongoing preliminary metallurgical testwork on the Colomac Gold
Project ("Colomac"). Findings 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 range from 96.5% on the lower-grade material and up
to 98.0% on the higher-grade rock (see press releases April 19, 2017 and February 21, 2018), representing a significant
increase in recovery over historic production results of 88.1%
(1994 to 1997).
Two initial bottle roll leach tests were carried out to assess
cyanide heap leach feasibility. Minus 12,700 micron (1.27
centimetre) material registered up to 81.8% recoveries on
lower-grade rock (1.81 grams per tonne gold "gpt Au",head
grade) and 57.50% on the higher-grade material (4.99 gpt Au). One
column leach test has been completed to date on higher-grade
mineralization posting a recovery of 34.30%. Such noted recovery
variability is not uncommon as significant fluctuations have also
been documented in recent metallurgical studies on other notable
northern deposits and is largely a function of the particle size
that interacts with the leachate.
Higher-Grade Testwork Highlights:
- Minimal variation in rock hardness of all test samples
indicates relatively homogeneous host rock;
- Favourable recoveries were achieved for all process options,
including, flotation, gravity separation, and heap leaching;
- 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 after gravity concentration
increased gold recoveries significantly up to 98.0%;
- Cyanide heap leach results show considerable variability
between testing methods and grade of material processed but fall
within expected performance range for crushed ore (recoveries
between 34.30% up to 81.8%).
Despite the variability, Colomac results convey a positive
indication of the deposit's heap leach potential, falling within
the expected performance range for crushed ore. Additional
metallurgical work is required to arrive at a statistically
relevant population of results for all deposit types, mineralized
zones and corresponding grade variations. As in the previous
sampling programs, testwork will be carried out on Colomac drill
core from recent drilling.
Dr. Michael Byron, President
& CEO commented, "Although at the early stages of metallurgical
testwork, the results to-date describe Colomac rock as exceptional
in terms of grind characteristics, gold recoveries, purity, and
responsiveness to all standard gold recovery technologies. We are
also encouraged by the preliminary heap leach bottle roll and
column test results. Although initial heap leach gold recoveries
show significant variability, other northern deposits including the
Fort Knox mine in Alaska, and
Yukon's Coffee Gold deposit, Eagle
Gold Project, and the Brewery Creek Mine all note variability in
their recoveries. To address this, metallurgical testing is planned
for 2018, that will cover some of the other mineralized zones, and
will include additional bottle roll and column leach testwork as we
continue to evaluate the potential heap leach option for the
project."
Metallurgical Testwork
Testing was completed at Bureau Veritas in Richmond, BC, and audited by Starkey &
Associates Inc. in Oakville,
Ontario. Studies to date have involved drill core mineral
process testwork on one higher grade sample from Zone 1.5, and on
lower-grade material consisting of three composite samples from
various areas of the Colomac Main Sill.
Three drill core bulk samples of similar mineralogical
characteristics, totalling 119.5 kilograms, of Colomac lower-grade
mineralization was collected from different regions and elevations
in the deposit to facilitate hardness testing (Table 1.0), and to
address spatial and grade variations of the quartz diorite host
rock (Table 2.0). Grinding test results indicate that all samples
exhibit a consistent high hardness and show minor variability, thus
they would present no milling issues. A master composite sample was
then blended for the metallurgical testwork. Recoveries are
summarized in Table 3.
To address the higher-grade mineralization, a single drill core
sample from Colomac's high-grade Zone 1.5, totalling 70 kilograms
of split drill core, was collected and submitted for identical
mineral process testwork as was conducted on the lower-grade
material.
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 Colomac Samples
|
|
|
Sample
|
Fire
Assay
|
Screen Metallics
Assay
|
Information
|
(g
Au/t)
|
(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
|
SG
Solids
|
WSDT
|
Sd-BWI
|
Information
|
|
(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
|
Average
|
2.71
|
13.15
|
14.48
|
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
|
95.5
|
90.7
|
GRAVITY
|
Fine
|
75
|
33.3
|
54.3
|
Medium
|
106
|
45.0
|
40.5
|
Coarse
|
150
|
25.9
|
42.8
|
*Crushed
Leach
|
Bottle Roll
Leach
|
12700
|
81.8
|
57.5
|
Column
Leach
|
12700
|
N/A
|
34.3
|
Ground
Leach
|
Whole Ore
|
150
|
96.5
|
96.4
|
Gravity +
Leach
|
106
|
96.4
|
98.0
|
*standard tests to determine preliminary heap leach
amenability
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 gold zones
within the mineralized sills, and to continue scrutinizing its heap
leach potential. 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, 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 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.
View original content with
multimedia:http://www.prnewswire.com/news-releases/nighthawk-provides-update-on-latest-colomac-metallurgical-testwork-300652551.html
SOURCE Nighthawk Gold Corp.