Dolly Varden has Commenced its 2019 Exploration and Drilling
Program
VANCOUVER, June 20, 2019 /CNW/ - Dolly Varden Silver
Corporation (TSXV: "DV" – OTCBB: "DOLLF") (the
"Company", or "Dolly Varden") is pleased to report
the results from a preliminary metallurgical study conducted by
Blue Coast Research on composite samples from the Dolly Varden
Deposit and the Torbrit Deposit. In addition, the 2019 exploration
program has commenced with the start of diamond drilling on the
Dolly Varden Property.
Preliminary metallurgical testing involved a variety of tests to
confirm that conventional methods of processing could be successful
in extracting the metals. Silver is the most important metal in the
Dolly Varden Mining Camp, however, several zones also contain
recoverable lead and zinc.
For the Dolly Varden Deposit composite sample, whole rock
cyanidation to extract silver proved to be the most effective
methodology. For the Torbrit Deposit composite sample, a mixture of
flotation to separate a lead-silver concentrate and a zinc
concentrate, followed by leaching of silver from the float tails,
proved to be the most effective extraction method, as described
below.
The 2019 exploration program will consist of approximately
10,000 metres of diamond drilling, lithogeochemical sampling,
prospecting and geological mapping. The drilling contractor is
Omineca Diamond Drilling Ltd. and the first drill hole of the
season commenced on June 16,
2019.
"These excellent metallurgical results further demonstrate
the successful extraction of a high percentage of silver, as well
as the extraction of base metals, which have not previously been
considered in the updated mineral resource estimates for the
project. We are looking forward to the 2019 drilling program as it
advances targets to the north of the current mineral resource
estimates," stated Gary Cope,
President and CEO.
In total, 20 separate flotation tests were conducted, which
included variations in grain size fractions, whole sulphide
flotation, separate Pb and Zn concentrate circuit tests, and
chemical additives. In addition, 6 whole rock cyanide leach tests
and 2 float tails cyanide leach tests were also conducted, along
with a Bond Ball Work Index test. A technical report containing the
detailed information on metallurgy is available on the Company
website.
Silver Recovery Percentages from Flotation Only, Cyanidation
on Float Tails, Combined Flotation & Cyanidation and Whole Rock
Cyanidation without Flotation
Deposit
|
Flotation
Only
|
Cyanidation on
Float Tails
|
Flotation +
Cyanidation
|
Whole Rock
Cyanidation
|
|
Lead Conc
|
Zinc Conc
|
|
|
|
Dolly
Varden
|
65
|
-
|
54
|
84
|
86
|
Torbrit
|
64
|
7
|
59
|
88
|
87
|
Silver and Base Metals Recovery Percentages from the Combined
Flotation + Cyanidation
Deposit
|
Test
Runs
|
Silver Recovery
%
|
Lead Recovery
%
|
Zinc Recovery
%
|
Dolly
Varden
|
F-14 +
CN-7
|
84
|
59
|
21
|
Torbrit
|
F-19 +
CN-8
|
88
|
78
|
70
|
For the Torbrit Deposit composite, the production of
separate lead and zinc flotation concentrates proved to be
relatively straightforward and a high-grade lead concentrate
containing the majority of the silver was produced. This
concentrate graded 58% Pb, 25,000 g/t Ag, and 3% Zn at lead and
silver recoveries of 76% and 64% respectively. The zinc concentrate
graded 36% Zn, 2,979 g/t Ag at a 64% Zn recovery. It is anticipated
that through further optimization, this zinc concentrate grade
could be increased to above 50%. Leaching of flotation tails from
the Torbrit Deposit composite yielded additional silver recovery.
Extraction of 59% of the silver in the tails brought the combined
flotation and cyanidation silver recoveries up to 88% for
Torbrit.
For the Dolly Varden Deposit composite, the higher
zinc content relative to lead made the production of a high-grade
lead concentrate more challenging. A lead concentrate was produced
containing 21% Pb, 22,000 g/t Ag and 23% Zn, at lead and silver
recoveries of 59% and 65% respectively. No separate zinc
concentrate was created in this test. Leaching of flotation tails
from the Dolly Varden Deposit composite yielded additional silver
recoveries. Extraction of 54% of the silver in the tails brought
the combined flotation and cyanidation silver recoveries up to 84%
for Torbrit.
A combination of flotation and leaching is currently the most
favourable processing option for the Torbrit Deposit material,
whereas whole rock leaching is preferable for the Dolly Varden
Deposit material given the slightly higher whole rock leach silver
recovery and the issues in separating lead and zinc in these
composites. Further delineation of mineralogical sub-zones
within deposits may be warranted.
Leach Kinematics
Whole rock leaching was also shown to be an effective process
option for the two composites, with bottle roll tests indicating
that a 92 hour leach residence time, with 3.0 g/l NaCN and a
relatively fine grind (~40um) will achieve up to 87% silver
extraction. The upside of whole rock leaching is that it is a
single process, whereas the downside is there is no recovery, nor
payment, for lead and zinc.
Head Grades of Composite Samples
Head grade composite sample characterization confirmed the Dolly
Varden Deposit composite grade to be 347 g/t Ag, 0.35 % Pb, 1.11 %
Zn and 7.67 % S. The Torbrit Deposit composite grade was 290 g/t
Ag, 0.55 % Pb, 0.39 % Zn and 8.32 % S.
Mineralogical analysis confirmed the Dolly Varden Deposit
contains on average 19% sulphide minerals, dominated by pyrite
(17%) and sphalerite (2%), with lessor amounts of galena (0.39%)
and acanthite (0.12%). The Torbrit Deposit composite was
overall lower in total sulphide content, averaging 4.3%, of which
pyrite (3.2%), galena (0.5%) and sphalerite (0.5%) make up the
majority, along with acanthite (0.06%), native silver (0.01%) and
polybasite (0.01%).
Bond Ball Work Index Test
A single Bond Ball Work Index Test was conducted on whole core
taken from the Torbrit Deposit. The Bond Ball Work Index was
calculated to be 9.5 KWh/tonne, suggesting that the Torbrit
material is relatively soft and that fine crushing would be
economically viable.
Technical Information and Qualified Persons
Metallurgical testing was conducted at the Parksville, BC, Canada, laboratories of Blue Coast Research
under the direction of David
Middleditch, B.Eng., ACSM.
In addition to the 'Independent Qualified Person' mentioned
above, Ben Whiting, P.Geo. FSEG,
Vice President of Exploration and Robert
van Egmond, P.Geo., Chief Geologist for Dolly Varden Silver
Corp., serve as 'Qualified Persons' as defined in NI 43-101, and
have approved the scientific and technical information contained in
this news release. To verify the technical information, both
Qualified Persons have visited the project site on numerous
occasions during the 2017 and 2018 field seasons, as well as the
latest site visit by Robert van
Egmond in June, 2019.
About Dolly Varden
Dolly Varden is a mineral exploration company focused on
exploration in northwestern British
Columbia. The Company has two projects, the namesake Dolly
Varden Silver Property and the nearby Big Bulk Copper-Gold
Property. Since December 2016, Dolly
Varden has been under the direction of management provided by the
experienced Belcarra Group Management Ltd. ("Belcarra
Group"). The Belcarra Group is comprised of highly qualified
mining and financial professionals.
Dolly Varden is also a member of the British Columbia Regional
Mining Alliance ("BCRMA"), a cooperative effort between First
Nations, Industry and the BC Provincial Government, to promote
mining activities and investment in the northwestern region.
Additional information about the Company and its activities may
be found on the Company's website www.dollyvardensilver.com and
under the Company's profile at www.sedar.com.
FORWARD-LOOKING STATEMENTS:
This release may contain forward-looking statements.
Forward-looking statements involve known and unknown risks,
uncertainties, and other factors which may cause the actual
results, performance, or achievements of Dolly Varden to be
materially different from any future results, performance, or
achievements expressed or implied by the forward-looking
statements. Forward looking statements or information relates to,
among other things, the results of previous field work and
programs, results of mineral resource estimate on the project, the
potential to grow the project, the potential to expand the
mineralization, the planning for further exploration work, the
ability to de-risk the potential exploration targets, and our
belief about the unexplored portion of the property. These
forward-looking statements are based on management's current
expectations and beliefs but given the uncertainties, assumptions
and risks, readers are cautioned not to place undue reliance on
such forward-looking statements or information. The Company
disclaims any obligation to update, or to publicly announce, any
such statements, events or developments except as required by
law.
Note: Mineral resources are not mineral reserves, and thus have
not demonstrated economic viability.
For additional information on risks and uncertainties, see the
Company's most recently filed annual management discussion &
analysis ("MD&A"), which is available on SEDAR at
www.sedar.com and on the Company's website at
www.dollyvardensilver.com. The risk factors identified in the
MD&A are not intended to represent a complete list of factors
that could affect the Company.
Neither the TSXV nor its Regulation Services Provider (as
that term is defined in the policies of the TSXV) accepts
responsibility for the adequacy or accuracy of this news
release.
SOURCE Dolly Varden Silver Corp.