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Denison Reports Postive Preliminary Testing Results for Gryphon Deposit

Denison Mines Corp. ("Denison" or the "Company") is pleased to announce the receipt of positive metallurgical test results from the Gryphon deposit, which support high rates of uranium recovery and the amenability of processing Wheeler River mine production at Denison's 22.5% owned McClean Lake mill.

"Having announced a significant increase in the estimated mineral resources at Wheeler River in late 2015, Denison is in the unique position of having a 60% interest in one of the largest and highest grade undeveloped uranium projects in the Athabasca Basin and an ownership interest in a state of the art uranium processing facility that is expected to have excess capacity in future years," said David Cates, President & CEO of Denison. "The preliminary testing results indicate Gryphon mine production will be suitable for processing at McClean Lake and will be incorporated into our upcoming PEA for Wheeler."

The McClean Lake mill is one of the most technologically advanced uranium mills in operation and is uniquely able to safely process the exceptionally high grades of Athabasca Basin ores without dilution. The McClean Lake mill is owned by the McClean Lake Joint Venture ("MLJV"), a joint venture between AREVA Resources Canada Inc. ("AREVA") (70%), Denison (22.5%) and OURD (Canada) Co. Ltd. (7.5%), and is operated by AREVA.

Positive Metallurgical Test Results from Gryphon

The Saskatchewan Research Council ("SRC"), under the guidance of Amec Foster Wheeler, completed a preliminary testing program on a composite sample of mineralization provided by Denison from the Gryphon deposit on the Wheeler River property. The objective of the tests carried out by SRC was to determine the preliminary leaching process, leach residue settling, raffinate composition, and purity of the U3O8 product, using test conditions that emulated the McClean Lake mill flowsheet. The 22.8 kilogram composite sample contained 3.36% U3O8 and was composed of drill cores from 10 separate drill holes spatially distributed throughout the Gryphon deposit resulting in 26 individual core assays. A comparison to the geological assay database indicated the composite sample is a fair representation of the Gryphon deposit on key parameters. Key highlights from the test work include:

  • A reasonable grind size of P100 = 300 micrometers achieved good uranium liberation;
  • Leaching tests demonstrated from 95.4% to 98.8% of the uranium can be extracted in 8 hours and from 98.6% to 99.2% can be extracted in 12 hours;
  • Reasonable reagent consumption levels in line with other Athabasca Basin ores;
  • Solvent extraction was effective in selectively extracting and purifying the uranium; and
  • No abnormal challenges are expected for effluent treatment based on raffinate composition.

Taken together, the results from the test samples show that a high purity U3O8 product can be produced, that meets all specifications from ASTM C967‐13 "Standard Specifications for Uranium Ore Concentrate". Amec Foster Wheeler has reviewed and approved the metallurgical sampling, analytical and test work results on behalf of Denison.

Wheeler River Property

The Wheeler River Property is host to both the Phoenix and Gryphon deposits. The Phoenix deposit is one of the highest grade undeveloped deposits in the world, estimated to include indicated mineral resources of 166,400 tonnes and 70.2 million pounds U3O8 at a grade of 19.1% U3O8. Additionally, the Phoenix deposit is estimated to include an inferred mineral resources of 8,600 tonnes and 1.1 million pounds U3O8 at a grade of 5.8% U3O8. The Gryphon deposit is hosted in basement rock, approximately three kilometres to the northwest of Phoenix, and is estimated to contain inferred mineral resources of 834,000 tonnes and 43.0 million pounds U3O8 at a grade of 2.3% U3O8. The Wheeler River project is a joint venture between Denison (60%), Cameco Corp. (30%), and JCU (Canada) Exploration Company Limited (10%). Denison is the operator and is currently evaluating the economics of co-developing the Gryphon and Phoenix deposits through the completion of a Preliminary Economic Assessment ("PEA").

Both the McClean Lake mill and the Wheeler River project are located in the infrastructure rich eastern portion of the Athabasca Basin in northern Saskatchewan. A provincial highway and power line run along the eastern edge of the Wheeler River property. This highway is used by other operations in the Athabasca Basin for transportation of uranium ores and similar highways run along the majority of the route between Wheeler River and the McClean Lake mill.

Qualified Person

The disclosure regarding the metallurgical test results contained in this news release was prepared and approved by Peter Longo, P. Eng, MBA, PMP, Denison's Vice-President, Project Development, who is a Qualified Person in accordance with the requirements of NI 43-101.

The disclosure of a scientific or technical nature regarding the Phoenix and Gryphon deposits contained in this news release was prepared by Dale Verran, MSc, Pr.Sci.Nat., Denison's Vice President, Exploration, who is a Qualified Person in accordance with the requirements of NI 43-101. For a description of the assay procedures and the quality assurance program and quality control measures applied by Denison, please see Denison's Annual Information Form dated March 5, 2015 filed under the Company's profile on SEDAR at


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