Denison Announces Discovery of High-Grade Uranium Mineralization at Moon Lake South

Denison Mines Corp. 

1100 – 40 University Ave 

Toronto, ON  M5J 1T1 

www.denisonmines.com 

PRESS RELEASE

Denison Announces Discovery of

High-Grade Uranium Mineralization at Moon Lake South

Toronto, ON – April 19, 2023. Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN:

NYSE American) is pleased to report that drill hole MS-23-10A intersected 1.38% eU3O8 over 8.7 metres

(0.05% eU3O8 cut-off), including a sub-interval grading 2.88% eU3O8 over 3.1 m, intersected approximately

30 m above the unconformity in the Athabasca sandstone, as part of t he recently completed winter

exploration program at the Moon Lake South property (“Moon South”).

Uranium mineralization was encountered in four of the six drill holes completed during the 2023 winter

exploration program, which was designed to eval uate the strike length of low-grade mineralized

occurrences identified in the 2021 and 2016 drill programs. Figure 1 and Figure 2 depict the location of the

Moon Lake South project, and the significant drill results on the project to date, respectively.

Andy Yackulic, P. Geo., Denison’s Director, Exploration, commented, “The discovery of high-grade

uranium mineralization at Moon Lake South gives further proof that the CR-3 trend has the potential

to host a large, high-grade unconformity-associated uranium deposit. The fact that this high-grade

material lies approximately 30 metres above the unconformity contact is very encouraging – as

perched mineralization like this is typically only found proximal to high-grade unconformity-hosted

deposits.”

David Cates, Denison’s President & CEO added, “The discovery of high-grade sandstone-hosted

uranium mineralization at Moon Lake South is a very exciting development for Denison, as our

Company’s recent field testing at the nearby 95%-owned Wheeler River project has illustrated the

potential viability of mining high-grade Athabasc a Basin sandstone-hosted uranium deposits via

In-Situ Recovery (ISR) mining.”

2023 Moon South Winter Exploration Program Highlights

The 2023 winter exploration program consisted of six completed diamond drill holes totalling 3,301 metres,

designed to evaluate the potential to expand the footprint of known mineralization discovered in 2016 and

2021 by testing conductivity anomalies identified fr om the 2022 stepwise moving loop electromagnetic

(SWML EM) survey.

Uranium mineralization was encountered in four of the six drill holes completed during the winter exploration

program. The mineralized intersections are summarized in Table 1. 

Table 1 – Mineralized Intersections – 2023 Moon Lake South Winter Exploration Drilling

Drill Hole Orientation

(azi./dip) From (m) To (m) Length (m) (1) eU 3O8 (%)(2,3)

MS-23-09 311°/-80.0° 408.45 408.65 0.2 0.06

MS-23-09 311°/-80.0° 451.45 451.95 0.5 0.12

MS-23-10A 311°/-81.5° 417.75 426.45 8.7 1.38

Including(4) 421.45 424.55 3.1 2.88

MS-23-10A 311°/-81.5° 430.85 432.05 1.2 0.07

MS-23-10AD1 311°/-81.5° 441.05 441.35 0.3 0.07

MS-23-11 309°/-81.5° 450.75 450.95 0.2 0.07

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Notes: (1) Lengths indicated represent the down-hole length of mineralized intersections.

(2) Radiometric equivalent U3O8 ("eU3O8") derived from a calibrated gamma downhole probe

(3) Mineralized interval is composited above a cut-off grade of 0.05% eU3O8

(4) Mineralized interval is composited above a cut-off grade of 2.00% eU3O8

The most significant mineralization was returned from hole MS-23-10A, which intersected a broad zone of

high-grade mineralization grading 1.38% eU 3O8 over 8.7 metres, associated with strong grey alteration,

located approximately 30 metres above the sub-Athabasca unconformity. Given the limited number of drill

holes completed during the winter program, the mine ralization discovered in MS-23-10A remains open in

multiple directions for future follow-up.

Radiometric Equivalent Grades, Sampling, Analysis and Data Verification

Following the completion of a drill hole, the hole is radiometrically logged using a downhole gamma probe,

which collects continuous readings of radioactivity along the length of the drill hole. Probe results are then

calibrated using an algorithm calculated from the comparison of probe results against geochemical

analyses in the area. The gamma-log results provide an immediate radiometric equivalent uranium value

(eU3O8%) for the hole, which, except in very high-g rade zones, is reasonably accurate. The Company

typically reports eU3O8, as a preliminary result and subsequently reports definitive assay grades following

sampling and chemical analysis of the mineralized drill core.

Assay sample intervals are generally 50 centimet res long, except where higher or lower-grade

mineralization boundaries fall within the interval. In that case, two 25 centimetre samples are collected.

Flank samples of 1.0 metre are always collected where mineralization is located. Systematic geochemistry

samples are collected every 10 metres down the hole.

All assayed core is split in half, with one half retain ed and the other sent to t he Saskatchewan Research

Council Geoanalytical Laboratory in Saskatoon for anal ysis. Control samples are routinely assayed with

each batch of core samples analyzed.

About Moon Lake South

The Moon Lake South project is a joint venture between Denison Mines Corp., which holds a 75% interest

in the property, and CanAlaska Uranium Ltd., which holds the remaining 25% interest. Denison acts as the

project operator.

The project lands are located in the southeastern part of the Athabasca basin, approximately 12 kilometres

southwest of Denison's Phoenix deposit, and 30 kilometres northwest of Cameco’s Key Lake Operation.

The property is accessible year-round via the Fox Lake tote road, allowing Denison’s exploration team to

use the nearby Wheeler River camp as a base of operations.

About Denison

Denison is a uranium exploration and development company with interests focused in the Athabasca Basin

region of northern Saskatchewan, Canada. The Compan y has an effective 95% interest in its flagship

Wheeler River Uranium Project, which is the largest undeveloped uranium project in the infrastructure rich

eastern portion of the Athabasca Basin region of northern Saskatchewan. Denison's interests in

Saskatchewan also include a 22.5% ownership interest in the McClean Lake joint venture, which includes

several uranium deposits and the McClean Lake uranium mill that is contracted to process the ore from the

Cigar Lake mine under a toll milling agreement, plus a 25.17% interest in the Midwest Main and Midwest A

deposits, and a 67.41% interest in the Tthe Heldeth Túé (“THT,” formerly J Zone) and Huskie deposits on

the Waterbury Lake property. The Midwest Main, Midw est A, THT and Huskie deposits are each located

within 20 kilometres of the McClean Lake mill.

Through its 50% ownership of 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%). Denis on's exploration portfolio includes further interests in properties

covering ~300,000 hectares in the Athabasca Basin region.

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Denison is also engaged in post-closure mine care and maintenance services through its Closed Mines

group, which manages Denison's reclaimed mine site s in the Elliot Lake region and provides related

services to certain third-party projects.

For more information, please contact

David Cates (416) 979-1991 ext 362

President and Chief Executive Officer

Mac McDonald (416) 979-1991 ext 242

Exec. Vice President & Chief Financial Officer

Follow Denison on Twitter @DenisonMinesCo

Qualified Persons

The technical information contained in this rele ase has been reviewed and approved by Mr. Andrew

Yackulic, P. Geo., Denison's Director, Exploration, who is a Qualified Person 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 c an be identified by the use of forward-look ing terminology such as ‘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’, ‘be achieved’ or ‘has

the potential to’.

In particular, this news release contains forward-looking information pertaining to the following: the interpretation of exploration results

and expectations with respect thereto, including the interpretation of the results from the Moon Lake South exploration program ; and

expectations regarding its joint venture ownership interests and the continuity of its agreements with its partners.

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 c ause the actual results, level of activi ty,

performance or achievements of Denison to be materially different from those expre ssed or implied by such forward-looking

statements. For example, the modelling and assumptions upon which the interpretation of results are based may not be maintained

after further testing or be representative of actual conditions. Denison believes that the expectations reflected in this forward-looking

information are reasonable but no assurance can be given that these expectations will pr ove to be accurate and results may diff er

materially from those anticipated in this forward-looking information. For a discussi on in respect of risks and other factors t hat could

influence forward-looking events, please refer to the factors discussed in Denis on’s Annual Information Form dated March 27, 2023

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 re liance on forward-looking statements. The forward-looking information contained i n

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 rel ease to conform such information to actual results or to changes in

Denison's expectations except as otherwise required by applicable legislation.

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Figure 1 – Moon Lake South Project - Location

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Figure 2 – Moon Lake South Project – 2023 Winter Drilling Results