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May 25, 2011

Excelsior Mining Corp. (TSX-V: MIN) (OTCQX: EXMGF) (Frankfurt: 3XS) (“Excelsior”) is pleased to announce the commencement of the initial hydrological test work on the Gunnison Copper Property located within the copper porphyry belt in southern Arizona. The program has been designed to determine the permeability of the mineralization and to confirm previous results that demonstrate that Gunnison can be mined using in-situ recovery (ISR) techniques.

The hydrological program will consist of drilling two holes up to 1200 feet deep within the North Star deposit to supplement the two historical hydrological holes drilled by Magma Copper Corporation in the mid 1990’s that gave encouraging results. This program will take several weeks to complete and will include geophysical logging, pump testing, water sampling and other tests to determine permeability and flow rates. This data will be combined with new metallurgical data (expected in late July) and the results from recent drilling to complete a Preliminary Economic Assessment expected in the third quarter of 2011.

“Hydrology is a key component of ISR,” says Stephen Twyerould, President and CEO of Excelsior. “We look forward to the results of this program and being able to show the investment community that ISR is a viable process.”

Gunnison currently contains a National Instrument (NI) 43-101 compliant inferred resource of 4.77 billion pounds of copper (787 million tons at 0.30% copper) which remains open for expansion (see news release dated November 2, 2010). An upgraded resource estimate is expected at the end of the second quarter of 2011.

Excelsior’s exploration work on the Gunnison Property is supervised by Stephen Twyerould, Fellow of AUSIMM, President and CEO of Excelsior and a Qualified Person as defined by NI 43-101. Mr. Twyerould has reviewed and is responsible for the technical information contained in this news release.

About Excelsior

Excelsior is an exploration and development company with a copper project located within the copper porphyry belt of Arizona. The Gunnison Copper Project is located close to the required infrastructure and with its in-situ recovery potential, is intended for near-term production. The Excelsior team consists of experienced professionals with proven track records of advancing projects towards production.

Further details about Excelsior can be found at: http://www.excelsiormining.com. Further information about the Gunnison Copper Project can be found in the technical report filed on SEDAR at www.sedar.com entitled: Gunnison Copper Project, Cochise County, Arizona, USA, Mineral Resource of the North Star and South Star Deposits dated June 2010.


"Stephen Twyerould"
President & CEO

T: 604-681-8030
F: 604-681-8039

Renmark Financial Communications Inc.
Barry Mire: This email address is being protected from spambots. You need JavaScript enabled to view it.
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Tel.: (514) 939-3989 or (416) 644-2020

Information set forth in this news release may involve forward-looking statements under applicable securities laws. Forward-looking statements are statements that relate to future, not past, events. In this context, forward-looking statements often address expected future business and financial performance, and often contain words such as "anticipate", "believe", "plan", "estimate", "expect", and "intend", statements that an action or event "may", "might", "could", "should", or "will" be taken or occur, or other similar expressions. All statements, other than statements of historical fact, included herein including, without limitation; statements about the production potential of the Gunnison Copper Project are forward-looking statements. By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors include, among others, the following risks: the need for additional financing; operational risks associated with mineral exploration; fluctuations in commodity prices; title matters; environmental liability claims and insurance; reliance on key personnel; the potential for conflicts of interest among certain officers, directors or promoters with certain other projects; the absence of dividends; competition; dilution; the volatility of our common share price and volume and the additional risks identified the management discussion and analysis section of our interim and most recent annual financial statement or other reports and filings with the TSX Venture Exchange and applicable Canadian securities regulations. Forward-looking statements are made based on management's beliefs, estimates and opinions on the date that statements are made and Excelsior undertakes no obligation to update forward-looking statements if these beliefs, estimates and opinions or other circumstances should change, except as required by applicable securities laws. Investors are cautioned against attributing undue certainty to forward-looking statements.

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 release, and no securities regulatory authority has either approved or disapproved of the contents of this release.










What is
In-Situ Mining