Sienna Commences Phase 2 Surface Exploration Program, Marathon North Platinum-Palladium Project, Ontario

Vancouver, British Columbia--(Newsfile Corp. - August 18, 2021) - Sienna Resources Inc. ("Sienna" or the "Company") (TSXV: SIE) (OTC Pink: SNNAF) (FSE: A1XCQ0) is pleased to announce that a second phase of surface exploration work has begun on their Marathon North Platinum-Palladium Property (the "Property") in Northern Ontario (see Figure 1), directly bordering Generation Mining Ltd.'s Marathon palladium project. This Phase 2 program, which will include geological mapping, prospecting, and sampling, follows up on the results from the first phase of surface exploration completed in late 2020 (see Company news release dated October 27, 2020) which identified a number of prospective locations with promising geology and minor sulphide mineralization.

Jason Gigliotti, President of Sienna Resources Inc., stated, "We are very pleased to now be underway on the Marathon North Platinum-Palladium Property in Ontario. This area is a world-class PGM region, and we are looking forward to what the next phase of operations will bring. We are also awaiting our drill results from the Bleka Gold Project in Norway and are now underway with our exploration program at our Kuusamo PGE Project in Finland. Also, a very significant development occurred yesterday in the Clayton Valley of Nevada, where Pure Energy Minerals Ltd. partner Schlumberger New Energy has received approval from the Bureau of Land Management (BLM) for a plan of operations covering the construction and operation of a pilot plant at Pure Energy's Clayton Valley, Nevada, lithium brine project. This project directly borders Sienna, and in fact Sienna's property lies directly inside of the Pure Energy land and is located in the deepest part of this basin. Clearly there are multiple projects that give Sienna shareholders potential for growth in the near and long term."

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Figure 1. General geology of the Coldwell Intrusive Complex and surrounding area, with the location of Sienna's four mining claim groups. The current exploration program will be targeting the westernmost claim group as a priority area, west of the Geordie Lake deposit.

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Sienna is one of the largest landholders within the Coldwell complex area, which is the largest alkaline intrusive complex in North America and hosts the Marathon PGM Deposit. According to Generation Mining's website, the Marathon PGM Deposit is one of the largest undeveloped platinum group metal mineral resources in North America, hosting several platinum group metal (PGM) and copper deposits, including the 8.7 million palladium-equivalent (PdEq) ounces in the Measured and Indicated categories and an additional 915,000 PdEq ounces in the Inferred category. On 7 January 2020, Generation Mining released a preliminary economic assessment (PEA) giving Marathon an after-tax net present value (NPV) of $871 million and an after tax payback of 2.5 years. Management cautions that past results or discoveries on properties in proximity to Sienna may not necessarily be indicative to the presence of mineralization on the Company's properties.

In other relevant news from the Clayton Valley in Nevada announced August 17, 2021, "Pure Energy Minerals Ltd. partner Schlumberger New Energy has received approval from the Bureau of Land Management (BLM) for a plan of operations covering the construction and operation of a pilot plant at Pure Energy's Clayton Valley, Nevada, lithium brine project. Schlumberger, Pure Energy's partner and operator of the Clayton Valley Project, has also received permit approval for the associated reclamation plan from the Nevada Division of Environmental Protection, Bureau of Mining Regulation and Reclamation. Construction and operation of the pilot plant are planned to occur at Pure Energy's Clayton Valley property located 40 miles southwest of Tonopah in Esmeralda County, Nevada, as approved by the BLM and Nevada authorities. In March 2021, Schlumberger New Energy announced its plans to develop a lithium extraction pilot plant at the Clayton Valley Project through its wholly owned subsidiary, NeoLith Energy (see Pure Energy news release of March 20, 2021)." Sienna has a brine project that is completely surrounded and located in the deepest section of Pure's property (see Clayton Valley map below). Management cautions that past results or discoveries on properties in proximity to Sienna may not necessarily be indicative to the presence of mineralization on the Company's properties.

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Clayton Valley Ownership Map

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About Sienna Resources Inc.

Sienna Resources is focused on exploring for and developing high-grade deposits in politically stable, environmentally responsible and ethical mining jurisdictions. Sienna is partnered with a New York Stock Exchange-listed mining company on two separate projects in Scandinavia including the past-producing Bleka and Vekselmyr orogenic gold projects in southern Norway which are both greenstone-hosted gold systems, and the Kuusamo Platinum Group Element (PGE) Project in Finland, directly bordering the LK Project being advanced by Palladium One Mining Inc. In North America, Sienna's projects include the Marathon North Platinum-Palladium Property in Northern Ontario, directly bordering Generation Mining Ltd.'s 8.7 million PdEq ounce Marathon deposit. Sienna also has the Clayton Valley Deep Basin Lithium Project in Clayton Valley, Nevada, home to the only lithium brine basin in production in North America, in the direct vicinity of Albemarle Corp.'s Silver Peak deposit and Tesla Motors Inc.'s Gigafactory. Management cautions that past results, discoveries or mineralization described on properties in proximity to Sienna may not necessarily be indicative of the presence of mineralization on the Company's properties.

The technical content of this news release was approved by Dr. Scott Jobin-Bevans (P.Geo.), a consulting geologist and qualified person as defined by National Instrument 43-101.

If you would like to be added to Sienna's email list please email info@siennaresources.com for information or join our twitter account at @SiennaResources.

Contact Information
Tel: 1.604.646.6900
Fax: 1.604.689.1733
www.siennaresources.com
info@siennaresources.com

"Jason Gigliotti"
President, Director
Sienna Resources Inc.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this press release.

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