dmc-pr20250716wregryphonw
Exhibit 99.1
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Denison Mines
Corp.
1100 – 40
University Ave
Toronto, ON M5J
1T1
www.denisonmines.com
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PRESS
RELEASE
Denison Announces Discovery of Additional High-Grade
Mineralization
at Gryphon and Reports Results from Successful Delineation
Program
Toronto, ON – July 16,
2025. Denison Mines Corp. (“Denison” or the
“Company”) (DML: TSX, DNN: NYSE American) is pleased to
announce the discovery of additional high-grade mineralization
approximately 40 metres outside of the previously estimated
mineralized domain associated with the D1 lens of the Gryphon
uranium deposit (“Gryphon”). Drill hole WR-837AD2
intersected 2.3 metres
at
1.69% eU3O8
including 0.5
metres at 5.48% eU3O8
in the in the down plunge direction
from the previously defined D1 lens. This area remains open
down-plunge and along strike to the northeast for further
expansion. Gryphon is situated approximately 3 km northwest of the
Company’s flagship Phoenix In-Situ Recovery
(“ISR”) uranium mine development project, on
Denison’s 95%-owned Wheeler River property in northern
Saskatchewan (see Figure 1).
The
discovery was made as part of a highly successful delineation drill
program carried out at Gryphon during the first half of 2025.
Results from the delineation drilling are expected to add
confidence to the previously estimated mineral resources for
Gryphon, having confirmed the current geological interpretation of
the deposit and intersecting uranium grades in line with expected
values.
Denison’s President and CEO, David Cates,
commented, “Our
2025 Gryphon delineation program was highly successful and achieved
each of the program’s key objectives – including (a)
increasing the density of drill testing within the A1 high-grade
domain and confirming the geological model, (b) collecting
additional geotechnical, metallurgical and hydrogeological samples
and information to support future project evaluation efforts, and
(c) initial testing of areas identified for possible expansion of
mineral resources that are outside of the mine design outlined in
the 2023 Pre-Feasibility Study
(“PFS”).
The delineation results demonstrate that Gryphon is an excellent
high-grade basement-hosted uranium deposit that justifies further
project development evaluation and de-risking. With a focus on
confirming the mineralization in the A-series of lenses, a limited
number of drill holes were designed to test for possible expansion
of the estimated mineral resource. As a result, we are excited that
drill hole WR-837AD2 encountered high-grade mineralization outside
of the existing mineralized domain in an area that remains wide
open for further expansion down-plunge and along strike. We are
currently developing plans to follow-up this result and test other
expansion targets.”
Gryphon Uranium Deposit
Gryphon was discovered by Denison in 2014 and is
estimated to contain Indicated Mineral Resources of 61.9 million
pounds U3O8
(1,643,000 tonnes an average grade of
1.7% U3O8),
plus Indicated Mineral Resources of 1.9 million pounds
U3O8
(73,000 tonnes at an average grade of
1.2% U3O8),
with an effective date of August 7, 2018.
Gryphon
is comprised of 24 primarily basement-hosted stacked lenses
referred to as the A-series, B-series, C-series, D-series and
E-series lenses, which are interpreted to be stacked to form a zone
of mineralization measuring approximately 280 metres long by 113
metres wide, with each lens having variable thicknesses and
generally plunging to the northeast and dipping to the southeast
(See Figure 2). Four high-grade domains have been established
within the A1 and D1 lenses. The A1 high-grade domain represents
40% of the total Indicated Mineral Resources estimated for the
deposit; whereas the combination of the three D1 high-grade domains
represent approximately 10% of the total Indicated Mineral
Resources.
Potential future development of the Gryphon
deposit has been assessed as an underground mining operation at a
PFS level in 2018 with a cost update completed in 2023. The
outcomes of the study highlight robust economics with an estimated
after-tax base-case Net Present Value (“NPV”) of $864.2
million and internal rate of return (“IRR”) of 37.6%,
based on estimated Probable Reserves of 49.7 million pounds
U3O8
(1,275,000 tonnes at 1.8%
U3O8),
a uranium selling price of USD$75/lb U3O8
($101.25/lb U3O8),
and an 8% discount rate. Gryphon’s cash operating costs are
estimated to be USD$12.75/lb U3O8,
and its all-in cost of production (including initial capital costs
of CAD$737.4 million) is estimated to be US$25.47/lb
U3O8.
Accordingly, Gryphon has the potential to be competitive with the
lowest cost uranium mining operations in the
world.
Discovery of Additional High-Grade Mineralization Associated with
the D1 lens
The
D series lenses were targeted for potential mineral resource
expansion in 2025 given their high-grade, structurally controlled
nature, and that previous drilling left the mineralization
partially open in the down-plunge and along-strike directions.
Prior to this program, no significant expansion drilling has
occurred proximal to Gryphon since 2018.
The
last drill hole of the 2025 program (WR-837AD2) encountered
high-grade uranium mineralization, which is interpreted to expand
the extent of the D1 zone by ~40 metres in the down-plunge
direction. This drill hole tested a 100-metre gap in the previous
drill hole spacing (see Figure 3) and justifies further follow-up
drilling to test to additional down-plunge extension as well as the
potential for along strike continuation. Drill hole WR-836 was also
completed in the expansion area and also encountered notable
uranium mineralization, which indicates the system is open along
strike to the north.
Denison reports its initial drilling results as
radiometric equivalent uranium (“%eU3O8")
from a calibrated, triple gamma, down-hole probe. All mineralized
intersections have been sampled for chemical U3O8
assay and final results will be
compiled following receipt of the data.
Table 1: Drill hole intercepts by lens
for WR-836 and WR-837AD2.1
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Drill Hole
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Lens
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From (m)
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To (m)
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Length (m)5
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%eU3O82
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WR-8361
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D13
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800.3
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800.8
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0.5
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0.40
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WR-837AD21
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D13
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834.6
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836.9
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2.3
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1.69
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(includes)4
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835.6
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836.1
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0.5
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5.48
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Notes:
1. Drill hole orientation (azimuth/dip) for WR-836 is
306.8o/-73.4o
and for WR-837AD2
is 311.1o/-71.0o
2. eU3O8 is radiometric equivalent uranium from a
calibrated total gamma down-hole probe. All intersections have been
sampled for chemical U3O8 assay
3. Intersection interval is
composited above a cut-off grade of 0.05% eU3O8
4. Intersection interval is
composited above a cut-off grade of 2.0% eU3O8
5. As most of
the drill holes are oriented steeply toward the northwest and the
basement mineralization is interpreted to dip moderately to the
southeast, the true thickness of the mineralization is expected to
be approximately 85% of the intersection lengths
2025 Delineation Drill Program Highlights
A
total of ~12,500 metres of diamond drilling was completed in
seventeen drill holes and multiple off cuts during the 2025
delineation program at Gryphon. Overall, the delineation program
confirmed the current geological interpretation of the deposit and
supported the grade-thickness (GT) assumptions in the resource
block model.
The
A1 lens was the primary focus of the drill program as the
high-grade and low-grade domains contain approximately 50% of the
estimated Indicated Mineral Resource for Gryphon. Several drill
holes intersected the A1 high-grade domain and established
additional continuity within the A-series lenses.
The
B and C series lenses are located below the A series within the
center of the deposit and were also intersected as part of the 2025
delineation program. Together the B and C series lenses account for
approximately 20% of the total estimated Indicated Mineral
Resources.
Several
drill holes encountered significant results, demonstrating the
high-grade nature of Gryphon, including the following results from
WR-831D1D2, which tested the primary lenses and returned the best
mineralized intercepts from the delineation program:
Table 2: Drill hole intercepts by lens
for WR-831D1D2.1
|
Lens
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From (m)
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To (m)
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Length (m)6
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%eU3O82
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A43
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655.6
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657.3
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1.7
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0.87
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A33
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664.9
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667.3
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2.4
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0.20
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A23
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682.5
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684.3
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1.8
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0.76
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A13
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689.3
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700.3
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11.0
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1.76
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(includes)4
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692.6
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694.4
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1.8
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3.85
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(includes)4
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695.3
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697.2
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1.9
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5.28
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B13
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701.2
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708.0
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6.8
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0.13
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B23
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713.0
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717.4
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4.4
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0.14
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B33
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721.0
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735.5
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14.5
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2.13
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(includes)4
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723.9
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725.7
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1.8
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6.38
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(includes)4
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727.1
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727.6
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0.5
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2.60
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(includes)4
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731.5
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734.0
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2.5
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6.16
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B3 (continued)3
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737.5
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743.8
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6.3
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0.91
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(includes)4
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740.1
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740.7
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0.6
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3.42
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Notes:
1. Drill hole orientation (azimuth/dip) 295.8o/-77.0o
2. eU3O8
is radiometric equivalent uranium from
a calibrated total gamma down-hole probe. All intersections have
been sampled for chemical U3O8
assay
3. Intersection interval is composited above a
cut-off grade of 0.05% eU3O8
4. Intersection interval is composited above a
cut-off grade of 2.0% eU3O8
5.
Intersections with less than 0.5 GT were left out of the table to
simplify the results
6. As most of
the drill holes are oriented steeply toward the northwest and the
basement mineralization is interpreted to dip moderately to the
southeast, the true thickness of the mineralization is expected to
be approximately 85% of the intersection lengths
Additional Data Collected for Future De-risking and Study
Work
Approximately
250 kg of whole-core samples were collected for metallurgical test
work. Metallurgical test programs are being developed to assess
uranium recoveries to advance the evaluation work completed to
support the 2018 and 2023 PFS.
Geotechnical
logging was completed on all drill holes and hydrogeological
information was collected from two of the drill holes which were
outfitted with vibrating wire piezometers (VWPs). The information
collected from these exercises is expected to increase the
understanding of different hydrogeological zones to support future
mine-design planning.
This
work adds to the extensive database of geological, hydrogeological,
geotechnical, and metallurgical data for Gryphon. This
site-specific data is expected to be used to validate certain key
assumptions in potential future technical studies further
evaluating the Gryphon deposit for underground mining.
About Wheeler River
Wheeler River is the largest undeveloped uranium project in the
infrastructure-rich eastern portion of the Athabasca Basin region,
in northern Saskatchewan. The project is host to the high-grade
Phoenix and Gryphon uranium deposits, discovered by Denison in 2008
and 2014, respectively, and is a joint venture between Denison (90%
and operator) and JCU (Canada) Exploration Company Limited ("JCU",
10%). In August 2023, Denison filed a technical report summarizing
the results of (i) the feasibility study completed for ISR mining
of the high-grade Phoenix uranium deposit and (ii) a cost update to
the 2018 Pre-Feasibility Study for conventional underground mining
of the basement-hosted Gryphon uranium deposit. More information on
the studies is available in the technical report titled "NI 43-101
Technical Report on the Wheeler River Project Athabasca Basin,
Saskatchewan, Canada" dated August 8, 2023, with an effective date
of June 23, 2023, a copy of which is available on Denison's website
and under its profile on SEDAR+ at www.sedarplus.ca and on EDGAR at
www.sec.gov/edgar.shtml.
Based on the respective studies, both deposits have the potential
to be competitive with the lowest cost uranium mining operations in
the world. Permitting efforts for the planned Phoenix ISR operation
commenced in 2019 and several notable milestones were achieved in
2024 with the submission of federal licensing documents and the
acceptance of the final form of the project's Environmental Impact
Statement by the Province of Saskatchewan and the Canadian Nuclear
Safety Commission.
About Denison
Denison is a uranium mining, exploration and development company
with interests focused in the Athabasca Basin region of northern
Saskatchewan, Canada. In addition to Denison's effective 95%
interest in its flagship Wheeler River Project, Denison's interests
in Saskatchewan also include a 22.5% ownership interest in the
McClean Lake Joint Venture ("MLJV"), which includes unmined uranium
deposits (planned for extraction via the MLJV's SABRE mining method
starting in 2025) and the McClean Lake uranium mill (currently
utilizing a portion of its licensed capacity to process the ore
from the Cigar Lake mine under a toll milling agreement), plus a
25.17% interest in the Midwest Joint Venture's Midwest Main and
Midwest A deposits, and a 70.55% interest in the Tthe Heldeth
Túé ("THT") and Huskie deposits on the Waterbury Lake
Property. The Midwest Main, Midwest A, THT and Huskie deposits are
located within 20 kilometres of the McClean Lake mill. Taken
together, Denison has direct ownership interests in properties
covering ~384,000 hectares in the Athabasca Basin
region.
Additionally, through its 50% ownership of JCU (Canada) Exploration
Company, Limited ("JCU"), Denison holds additional interests in
various uranium project joint ventures in Canada, including the
Millennium project (JCU, 30.099%), the Kiggavik project (JCU,
33.8118%), and Christie Lake (JCU, 34.4508%).
In 2024, Denison celebrated its 70th year in uranium mining,
exploration, and development, which began in 1954 with Denison's
first acquisition of mining claims in the Elliot
Lake region of northern Ontario.
For more information, please contact
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David
Cates
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(416) 979-1991
ext. 362
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President and Chief Executive
Officer
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Geoff
Smith
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(416) 979-1991 ext.
358
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Vice
President Corporate Development & Commercial
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Follow
Denison on X (formerly Twitter)
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@DenisonMinesCo
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Qualified Persons
The technical information contained in this press release has been
reviewed and approved by Chad Sorba, P.Geo., Denison's Vice
President Technical Services & Project Evaluation, who is a
Qualified Persons in accordance with the requirements of NI
43-101.
Cautionary Statement Regarding Forward-Looking
Statements
Certain information contained in this news release constitutes
‘forward-looking information’, within the meaning of
the applicable United States and Canadian legislation, concerning
the business, operations and financial performance and condition of
Denison. Generally, these forward-looking statements can be
identified by the use of forward-looking terminology such as
‘potential’, ‘plans’,
‘expects’, ‘budget’,
‘scheduled’, ‘estimates’,
‘forecasts’, ‘intends’,
‘anticipates’, or ‘believes’, or the
negatives and/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’.
In particular, this news release contains forward-looking
information pertaining to the following: scope, objectives and
interpreted results of the Gryphon delineation program; future
plans, including potential future exploration potential and
metallurgical test programs; and expectations regarding its joint
venture ownership interests and the continuity of its agreements
with its partners and third parties. Statements relating to
‘mineral reserves’ or ‘mineral resources’
are deemed to be forward-looking information, as they involve the
implied assessment, based on certain estimates and assumptions that
the mineral reserves and mineral resources described can be
profitably produced in the future.
Forward looking statements are based on the opinions and estimates
of management as of the date such statements are made, and they are
subject to known and unknown risks, uncertainties and other factors
that may cause the actual results, level of activity, performance
or achievements of Denison to be materially different from those
expressed or implied by such forward-looking statements. For
example, the modelling and assumptions upon which the plans for
Wheeler River are based may not be maintained after further work is
completed. In addition, Denison may decide or otherwise be required
to discontinue testing, evaluation and other work if it is unable
to maintain or otherwise secure the necessary resources (such as
testing facilities, capital funding, regulatory approvals, etc.).
Denison believes that the expectations reflected in this
forward-looking information are reasonable but no assurance can be
given that these expectations will prove to be accurate and results
may differ materially from those anticipated in this
forward-looking information. For a discussion in respect of risks
and other factors that could influence forward-looking events,
please refer to the factors discussed in Denison’s Annual
Information Form dated March 28, 2025 or subsequent quarterly
financial reports under the heading ‘Risk Factors’.
These factors are not, and should not be construed as being
exhaustive.
Accordingly, readers should not place undue reliance on
forward-looking statements. The forward-looking information
contained in this news release is expressly qualified by this
cautionary statement. Any forward-looking information and the
assumptions made with respect thereto speaks only as of the date of
this news release. Denison does not undertake any obligation to
publicly update or revise any forward-looking information after the
date of this news release to conform such information to actual
results or to changes in Denison's expectations except as otherwise
required by applicable legislation
Figure 1: Wheeler River Property Map
Figure 2: Plan View of Gryphon Deposit
Figure 3: Location and Interpretation of Drill Holes WR-836 and
WR-837AD2
Inclined Longitudinal Section (left) Isometric Cross-section
(right)
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