DML.TO · 2017-11-02 12:00:00

Denison Extends High-Grade Unconformity Mineralization Near the Gryphon Deposit with 4.3% EU 3O8 over 4.3 Metres and Completes Summer Drilling at Wheeler

Drill Results Exploration Programs

Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

@DenisonMinesCo

PRESS RELEASE

DENISON EXTENDS HIGH-GRADE UNCONFORMITY MINERALIZATION

NEAR THE GRYPHON DEPOSIT WITH 4.3% eU 3O8 OVER 4.3 METRES

AND COMPLETES SUMMER DRILLING AT WHEELER

Toronto, ON – November 2, 2017 Denison Mines Corp. (“Denison” or the “Company”) (TSX: DML) (NYSE

MKT: DNN) (NYSE American: DNN) is pleased to report the extension of new high-grade unconformity-

hosted uranium mineralization located up-dip and ap proximately 250 metres along strike to the northeas t

of the basement-hosted Gryphon deposit, on the Comp any’s 60% owned Wheeler River project.

Preliminary radiometric equivalent grades (“eU 3O8”) from drill hole WR-670D2 are highlighted by an interval

of 4.3% eU 3O8 over 4.3 metres, from mineralization occurring imm ediately above the sub-Athabasca

unconformity. This result adds to previous unconfor mity mineralized intercepts that include 5.0% eU 3O8

over 4.7 metres in drill hole WR-689D3 and 1.2% eU 3O8 over 1.4 metres in drill hole WR-690D3 (see

Denison’s press release dated August 30, 2017). The new zone of “E series” unconformity mineralization

now extends approximately 80 metres horizontally al ong the unconformity and remains open along strike

to the northeast and southwest.

In addition, after nearly six months of field activ ities, Denison is pleased to report that the summer 2017

drilling program at Wheeler River has now been conc luded, following the completion of a further 30 dri ll

holes totalling 12,466 metres. Preliminary radiome tric grades for these results are reported herein a nd

represent a strong finish, to an extended summer ex ploration program at Wheeler, with continued

exploration success on multiple fronts. Importantly, these results also represent the final batch of drill holes

to be completed ahead of the planned update to the Company’s resource estimate for the Gryphon deposit

and the Wheeler River project.

Highlights from the final 30 drill holes include:

• Extension of the E series lenses: Additional mineralized intervals in the E series lenses were returned

at the unconformity in drill hole WR-670D2 (4.3% eU3O8 over 4.3 metres) and WR-657D3 (0.86% eU 3O8

over 2.2 metres), as well as in the upper basement in drill hole WR-646D2 (4.6% eU 3O8 over 1.5 metres)

and WR-646D4 (1.1% eU 3O8 over 7.6 metres). The E series lenses occur outsid e of the current

resources estimated for the Gryphon deposit, remain open along strike to the northeast and southwest,

and now have an unconformity and upper basement extent of 80 and 350 metres, respectively.

• Continued expansion of high-grade within the D seri es lenses: Intersections of 4.9% eU 3O8 over

1.0 metre (drill hole WR-621D5), 1.6% eU 3O8 over 2.5 metres (drill hole WR-657D2), and 2.0% eU 3O8

over 1.3 metres (drill hole WR-657D3), have added t o several previous high-grade results within the D

series lenses. During the summer program, a signif icant lens of high-grade mineralization has been

delineated amongst the D series lenses by infill drilling on an approximate 25 x 25 metres spacing. The

high-grade lens measures up to 150 metres along str ike, approximately 240 metres along dip, with

interpreted true thicknesses between approximately 2 and 20 metres. All D series lens mineralization

occurs outside of the current resources estimated for the Gryphon deposit.

• Continued expansion of the A and B series lenses: Drill holes located down-dip and up-dip of the

extent of the A and B series lenses, as defined by the current resources estimated for the Gryphon

deposit, returned highlight intersections of 4.0% e U 3O8 over 3.1 metres (drill hole WR-681AD3) and

4.0% eU 3O8 over 5.2 metres (drill hole WR-624D3). The holes w ere located approximately 25 metres

from previous holes with the potential to add indicated resources to the Gryphon deposit.

• Completion of the definition drilling program: Definition drilling designed to upgrade the current

inferred resources of the Gryphon deposit (A, B and C series lenses) to an indicated level of confidence

has now been completed with the final four drill holes, of the 42 drill hole program, successfully reaching

their respective targets. Results continue to show good consistency with the inferred grade model.

Dale Verran, Denison’s Vice President Exploration, commented, “The summer drilling program at Wheeler

River has produced exceptional results with over 90 % of the holes completed returning significant

mineralization. The sheer number of high-grade and thick intersections, inside and outside the current

Gryphon resource area, indicate potential to increa se both the confidence and size of the Gryphon

deposit. An updated independent resource estimate, in accordance with NI 43-101, is planned for later

this year once the final batch of assay results is received. Looking ahead to 2018, our exploration te am

is excited to continue with exploration near Grypho n. The mineralizing system continues to impress as

new zones continue to be added – most recently with the E series lenses. The deposit remains open in

numerous areas with excellent prospects for further growth.”

Summer 2017 Drilling Program Completed

The primary objectives of the summer 2017 explorati on program were to increase the confidence of the

Gryphon resource to an indicated level, and to expa nd the overall size of the estimated resources, ahe ad

of an updated resource estimate, scheduled for late r in the year, and the Pre-Feasibility Study ("PFS" ),

scheduled for 2018. As a result, the summer program included a total of 64 drill holes (totalling 29,8 23

metres) targeted within and in the immediate vicini ty of the Gryphon deposit. The large majority of d rill

holes (59) were completed as ‘daughter’ holes drill ed from part way down ‘parent holes’, which were

previously drilled from surface. Included in the fi nal 30 drill holes is also a single shaft pilot hol e, totalling

600 metres, which was completed near the Gryphon deposit as part of field activities related to the Wheeler

River PFS.

Illustrative Figures and Further Details

A plan map of the Gryphon A, B, C, D and E series l enses is provided in Figure 1. The inset on Figure 1

shows a schematic cross section of the A, B, C, D a nd E series lenses and their respective inclined

longitudinal section windows (as shaded rectangles) . Figures 2 to 6 provide inclined longitudinal sect ions

of the Gryphon A, B, C, D and E series lenses respe ctively. Figure 7 provides a plan map of the

mineralization located at, or immediately above, the sub-Athabasca unconformity which forms part of the E

series lenses.

The modelled mineralized lenses shown in Figures 1 to 6 are defined using a 0.05% U3O8 grade shell and

minimum thickness of two metres and have been updated following receipt of the winter 2017 assay results.

There is no certainty that the modelled mineralized lenses shown will constitute future mineral resour ces

and they may be subject to modifications as further drilling data becomes available.

Further details regarding the Gryphon deposit and t he current mineral resource estimates are provided in

the NI 43-101 Technical Report for the Wheeler Rive r project titled “Preliminary Economic Assessment for

the Wheeler River Uranium Project, Saskatchewan, Ca nada" dated April 8, 2016 with an effective date of

March 31, 2016. A copy of this report is availabl e on Denison’s website and under its profile on SEDAR

at www.sedar.com and on EDGAR at www.sec.gov/edgar.shtml.

Detailed Radiometric Equivalent Probe Results

The following tables provide the radiometric equivalent probe results from the final 30 drill holes completed

during the summer 2017 exploration program at Wheeler River.

Table 1: Radiometric equivalent probe results for drill holes targeting the Gryphon D and E series lenses

Section Drill Hole From (m) To (m) Length (m) 5 eU 3O8(%) 1,2,4 Lens Designation

5125GP

WR-646D1 557.9 558.9 1.0 0.33 E Series

and 586.8 588.6 1.8 1.0 E Series

including 3 587.3 588.3 1.0 1.4 E Series

and 686.5 687.5 1.0 0.36 D Series

5150GP

WR-621D4 No significant mineralization

WR-621D5 750.7 751.7 1.0 0.11 D Series

WR-646D2 584.7 586.2 1.5 4.6 E Series

including 3 584.9 586.0 1.1 6.2 E Series

WR-646D3 Not probed

WR-646D4 559.1 560.1 1.0 0.15 E Series

and 578.5 579.5 1.0 0.10 E Series

and 580.2 581.2 1.0 0.27 E Series

and 585.7 593.3 7.6 1.1 E Series

including 3 585.8 586.8 1.0 3.4 E Series

including 3 590.0 591.5 1.5 2.1 E Series

and 664.4 665.4 1.0 0.15 E Series

and 697.0 698.1 1.1 4.4 D Series

including 3 697.1 698.1 1.0 4.9 D Series

WR-646D5 578.7 579.9 1.2 0.97 E Series

including 3 578.7 579.7 1.0 1.1 E Series

and 586.1 587.1 1.0 0.14 E Series

5250GP

WR-657D3 559.3 560.3 1.0 0.11 E Series

and 561.4 562.4 1.0 0.23 E Series

and 564.4 566.6 2.2 0.86 E Series

including 3 564.5 565.5 1.0 1.7 E Series

and 664.5 665.5 1.0 0.24 E Series

and 677.6 678.6 1.0 0.22 E Series

and 693.4 694.4 1.0 0.92 D Series

and 701.3 702.6 1.3 2.0 D Series

including 3 701.4 702.4 1.0 2.5 D Series

5275GP

WR-657D2 586.4 587.4 1.0 0.20 E Series

and 624.3 625.3 1.0 0.11 E Series

and 680.1 682.6 2.5 1.6 D Series

including 3 680.5 682.4 1.9 2.0 D Series

and 700.4 701.4 1.0 0.12 D Series

WR-670D2 3 544.6 548.9 4.3 4.3 E Series

and 553.6 555.3 1.7 0.13 E Series

and 569.7 570.7 1.0 0.39 E Series

and 681.3 682.3 1.0 0.18 D Series

Notes:

1. eU 3O8 is radiometric equivalent U3O8 derived from a calibrated total gamma downhole probe. eU 3O8 results are preliminary

in nature and all mineralized intervals will be sampled and submitted for chemical U3O8 assay.

2. Intersection interval is composited above a cut- off grade of 0.1% eU 3O8 unless otherwise indicated.

3. Intersection interval is composited above a cut- off grade of 1.0% eU 3O8.

4. Composites are compiled using 1.0 metre minimum ore thickness and 2.0 metres maximum waste.

5. As the drill holes are oriented steeply toward t he northwest the true thickness of both the basemen t and unconformity

mineralization is expected to be approximately 75% of the intersection lengths (the basement mineralization is interpreted

to dip moderately to the southeast and the unconformity mineralization is interpreted to be flat-lying).

Table 2: Radiometric equivalent probe results for Gryphon deposit A, B, C definition and expansion drill

holes

Section Drill Hole From (m) To (m) Length (m) 5 eU 3O8(%) 1,2,4 Lens Designation

4775GP WR-679D1 No significant mineralization

4800GP WR-584BD2 631.2 632.2 1.0 0.11 B Series

4875GP WR-580D2 No significant mineralization

4900GP

WR-681AD1 No significant mineralization

WR-580D1 613.2 614.6 1.4 0.16 A Series

4925GP

WR-681AD2 698.9 699.9 1.0 0.26 A Series

and 718.3 719.9 1.6 1.3 A Series

including 3 718.6 719.6 1.0 1.9 A Series

and 725.8 727.4 1.6 1.7 A Series

including 3 726.1 727.2 1.1 2.2 A Series

and 785.1 786.1 1.0 0.54 C Series

WR-673D1 612.6 615.5 2.9 1.1 A Series

including 3 614.5 615.5 1.0 2.8 A Series

and 648.7 649.7 1.0 0.17 B Series

and 680.9 681.9 1.0 0.15 C Series

and 697.3 698.3 1.0 0.28 C Series

and 699.6 700.6 1.0 0.15 C Series

WR-681AD3 705.6 709.0 3.4 0.41 A Series

and 714.1 717.2 3.1 4.0 A Series

including 3 715.3 717.0 1.7 6.9 A Series

and 724.5 725.5 1.0 0.29 B Series

and 781.8 782.8 1.0 0.29 C Series

4950GP

WR-572D4 641.7 642.7 1.0 0.78 A Series

and 644.3 645.3 1.0 0.11 A Series

and 657.5 658.5 1.0 0.38 B Series

and 665.5 667.4 1.9 0.21 B Series

and 706.7 707.7 1.0 0.19 C Series

4975GP

WR-572D3 643.3 644.4 1.1 0.23 A Series

and 668.5 669.5 1.0 0.17 B Series

and 685.1 686.1 1.0 0.13 B Series

WR-624D2 632.9 633.9 1.0 0.32 A Series

and 634.3 635.3 1.0 0.10 A Series

and 636.5 637.5 1.0 0.19 A Series

and 642.0 643.0 1.0 0.10 A Series

and 647.7 651.1 3.4 1.1 A Series

including 3 649.8 650.8 1.0 2.7 A Series

and 669.6 670.7 1.1 0.33 B Series

and 677.5 678.7 1.2 0.46 B Series

and 731.9 733.5 1.6 1.0 C Series

including 3 732.3 733.3 1.0 1.6 C Series

5000GP

WR-624D1 628.7 629.7 1.0 0.79 A Series

and 635.2 636.2 1.0 0.11 A Series

and 638.0 639.0 1.0 0.31 A Series

and 653.2 654.2 1.0 0.83 A Series

and 656.2 657.9 1.7 1.0 A Series

including 3 656.2 657.2 1.0 1.6 A Series

and 662.2 666.3 4.1 0.57 A Series

including 3 663.4 664.4 1.0 1.3 A Series

and 691.6 695.3 3.7 0.31 B Series

and 737.5 742.0 4.5 0.56 C Series

and 745.8 748.1 2.3 0.69 C Series

and 797.2 799.3 2.1 0.23 C Series

WR-578D1 707.4 708.4 1.00 0.59 A Series

and 758.0 759.7 1.7 2.5 A Series

including 3 758.5 759.5 1.0 3.9 A Series

and 766.8 768.0 1.2 0.42 B Series

WR-624D3 631.1 632.1 1.0 0.20 A Series

and 636.4 640.2 3.8 0.54 A Series

including 3 637.2 638.2 1.0 1.3 A Series

and 660.9 666.1 5.2 4.0 B Series

including 3 663.8 665.9 2.1 9.3 B Series

and 669.2 670.3 1.1 0.28 B Series

and 720.9 721.9 1.0 0.40 C Series

and 738.6 741.2 2.6 0.69 C Series

5025GP

WR-560D1 669.6 672.4 2.8 0.39 A Series

and 675.2 676.2 1.0 0.24 A Series

and 720.4 721.4 1.0 0.24 B Series

and 759.2 760.4 1.2 3.8 C Series

including 3 759.3 760.3 1.0 4.5 C Series

WR-560D2 675.0 676.0 1.0 0.38 B Series

and 696.8 697.8 1.0 0.10 B Series

and 729.2 730.5 1.3 0.13 C Series

and 744.9 745.9 1.0 0.16 C Series

and 747.8 754.7 6.9 0.76 C Series

including 3 747.9 748.9 1.0 1.0 C Series

including 3 750.4 751.4 1.0 2.0 C Series

including 3 752.0 753.0 1.0 1.2 C Series

5075GP

WR-568D3 687.9 690.2 2.3 0.18 A Series

and 725.3 726.3 1.0 0.14 A Series

and 753.0 754.3 1.3 0.54 C Series

5125GP

WR-600D2 723.3 725.2 1.9 0.35 A Series

and 729.1 730.1 1.0 0.20 B Series

and 732.2 733.4 1.2 0.12 B Series

and 741.1 743.2 2.1 0.11 B Series

5150GP WR-600D3 710.4 714.5 4.1 0.21 A Series

and 720.8 721.8 1.0 0.21 A Series

and 732.7 733.8 1.1 0.18 B Series

and 738.2 739.2 1.0 0.16 B Series

Notes:

1. eU 3O8 is radiometric equivalent U3O8 derived from a calibrated total gamma downhole probe. eU 3O8 results are preliminary

in nature and all mineralized intervals will be sampled and submitted for chemical U3O8 assay.

2. Intersection interval is composited above a cut- off grade of 0.1% eU 3O8 unless otherwise indicated.

3. Intersection interval is composited above a cut- off grade of 1.0% eU 3O8.

4. Composites are compiled using 1.0 metre minimum ore thickness and 2.0 metres maximum waste.

5. As the drill holes are oriented steeply toward t he northwest and the basement mineralization is interpreted to dip moderately

to the southeast, the true thickness of the mineralization is expected to be approximately 75% of the intersection lengths.

Qualified Persons and Data Quality

Dale Verran, MSc, P.Geo, Pr.Sci.Nat., Denison's Vice President, Exploration, who is a Qualified Person in

accordance with the requirements of NI 43-101 has r eviewed and approved the technical information

contained in this release. The Company currently re ports preliminary radiometric equivalent grades

("eU 3O8"), derived from a calibrated downhole total gamma probe, during its exploration programs and

subsequently reports definitive assay grades follow ing sampling and chemical analysis of the mineraliz ed

drill core. Radiometric equivalent probe results ar e subject to verification procedures by qualified p ersons

employed by Denison prior to disclosure. For furthe r details on the total gamma downhole probe methods

employed by Denison, QAQC procedures and data verif ication procedures please see Denison's Annual

Information Form dated March 23, 2017 filed under the Company's profile on SEDAR (www.sedar.com).

About Wheeler River

Wheeler River is the largest undeveloped high-grade uranium project in the infrastructure rich eastern

portion of the Athabasca Basin region, in northern Saskatchewan. The project is a joint venture betwe en

Denison (60% and operator), Cameco Corp. (“Cameco”) (30%), and JCU (Canada) Exploration Company

Limited (“JCU”) (10%), and is host to the high-grade Gryphon and Phoenix uranium deposits discovered by

Denison in 2014 and 2008, respectively. The Gryphon deposit is hosted in basement rock and is currentl y

estimated to contain inferred resources of 43.0 mil lion pounds U 3O8 (above a cut-off grade of 0.2% U 3O8)

based on 834,000 tonnes of mineralization at an ave rage grade of 2.3% U 3O8. The Phoenix unconformity

deposit is located approximately 3 kilometres to th e southeast of Gryphon and is estimated to include

indicated resources of 70.2 million pounds U 3O8 (above a cut-off grade of 0.8% U 3O8) based on 166,000

tonnes of mineralization at an average grade of 19.1% U 3O8, and is the highest grade undeveloped known

uranium deposit in the world.

On April 4th, 2016, Denison announced the results of a Preliminary Economic Assessment (“PEA”) for the

Wheeler River Project, which considers the potentia l economic merit of co-developing the high-grade

Gryphon and Phoenix deposits as a single undergroun d mining operation. The PEA returned a base case

pre-tax Internal Rate of Return ("IRR") of 20.4% ba sed on the current long term contract price of uran ium

(US$44.00 per pound U 3O8), and Denison's share of estimated initial capital expenditures ("CAPEX") of

CAD$336M (CAD$560M on 100% ownership basis). Explo ration results from the subsequent drilling

programs have not been incorporated into the resour ce estimate or the PEA. The PEA is preliminary in

nature and includes inferred mineral resources that are considered too speculative geologically to have the

economic considerations applied to them to be categ orized as mineral reserves, and there is no certain ty

that the preliminary economic assessment will be realized. Mineral resources are not mineral reserves and

do not have demonstrated economic viability. On Jul y 19th, 2016 Denison announced the initiation of a

Pre-Feasibility Study ("PFS") for the Wheeler River property and the complimentary commencement of an

infill drilling program at the Gryphon deposit to b ring the inferred resources to an indicated level o f

confidence.

As previously announced on January 10, 2017, Deniso n has entered into an agreement with its Wheeler

River Joint Venture partners, Cameco and JCU, to fu nd 75% of Joint Venture expenses in 2017 and 2018

(ordinarily 60%) in exchange for an increase in Denison's interest in the project to up to approximately 66%.

Under the terms of the agreement, Cameco will fund 50% of its ordinary 30% share in 2017 and 2018, and

JCU is expected to continue to fund its 10% interest in the project.

About Denison

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

region of northern Saskatchewan, Canada. In addition to its 60% owned Wheeler River project, which hosts

the high-grade Phoenix and Gryphon uranium deposits , Denison's exploration portfolio consists of

numerous projects covering approximately 347,000 he ctares in the Athabasca Basin region, including

327,000 hectares in the infrastructure rich eastern portion of the Athabasca Basin. Denison's interest s in

Saskatchewan also include a 22.5% ownership interest in the McClean Lake joint venture (“MLJV”), which

includes several uranium deposits and the McClean L ake uranium mill, which is currently processing ore

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

a 64.22% interest in the J Zone deposit on the Wate rbury Lake property. Both the Midwest and J Zone

deposits are located within 20 kilometres of the McClean Lake mill.

Denison is also engaged in mine decommissioning and environmental services through its Denison

Environmental Services division and is the manager of Uranium Participation Corp., a publicly traded

company which invests in uranium oxide and uranium hexafluoride.

For more information, please contact

David Cates (416) 979-1991 ext. 362

President and Chief Executive Officer

Sophia Shane (604) 689-7842

Investor Relations

Follow Denison on Twitter @DenisonMinesCo

Cautionary Statement Regarding Forward-Looking Statements

Certain information contained in this press release constitutes "forward-looking information", within the meaning of the United States

Private Securities Litigation Reform Act of 1995 an d similar Canadian legislation concerning the busin ess, operations and financial

performance and condition of Denison.

Generally, these forward-looking statements can be identified by the use of forward-looking terminolog y 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 press release contains forward-looking information pertaining to the following: exploration (including

drilling) and evaluation activities, plans and objectives; potential mineralization of drill targets; the estimates of Denison's mineral resources

and the results of its PEA; plans and objectives with respect to updating its resource estimates and preparing a PFS; and Denison’s

percentage in its properties and its plans and agreements with its joint venture partners, as applicable. 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 forward-looking statements. 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 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 23, 2017 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 press 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 press release. Denison does not undertake

any obligation to publicly update or revise any forward-looking information after the date of this press release to conform such information

to actual results or to changes in Denison's expectations except as otherwise required by applicable legislation .

Cautionary Note to United States Investors Concerning Estimates of Measured, Indicated and Inferred Mineral Resources: This

press release may use the terms “measured”, “indicated” and “inferred” mineral resources. United States investors are advised that while

such terms are recognized and required by Canadian regulations, the United States Securities and Exchange Commission does not

recognize them. “Inferred mineral resources” have a great amount of uncertainty as to their existence, and as to their economic and legal

feasibility. It cannot be assumed that all or any part of an inferred mineral resource will ever be upgraded to a higher category. Under

Canadian rules, estimates of inferred mineral resources may not form the basis of feasibility or other economic studies. United States

investors are cautioned not to assume that all or any part of measured or indicated mineral resources will ever be converted into mineral

reserves. United States investors are also cautioned not to assume that all or any part of an inferred mineral resource exists, or is

economically or legally mineable.

Figure 1: Plan map of the northeast plunging Gryphon mineralized lenses projected up to the simplified basement geology at the

sub-Athabasca unconformity.

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