Hydrology Tests Confirms Suitable Conditions for In-Situ Recovery at Excelsior's Gunnison Project

VANCOUVER, BRITISH COLUMBIA--(Marketwire - Sept. 6, 2011) - Excelsior Mining Corp. (TSX VENTURE:MIN)(OTCQX:EXMGF)(PINK SHEETS:EXMGF)(FRANKFURT:3XS) ("Excelsior") is pleased to announce results from two comprehensive hydrological tests conducted at the North Star Deposit. The results generated hydrological conductivities in the range expected for a fractured deposit and show the deposit is suitable for in-situ recovery (ISR). The North Star Deposit is part of the Gunnison Copper Property located within the copper porphyry belt in southern Arizona.

"We are very pleased with the results from this initial hydrological testing. We have successfully achieved another milestone in demonstrating suitable hydrological conditions for ISR at the North Star Deposit," says Stephen Twyerould, President and CEO of Excelsior. "These results will be combined with new metallurgical data to complete a Preliminary Economic Assessment expected later this year. Further hydrological and metallurgical testing will be carried out as we continue driving our Project towards production."

The North Star Deposit currently contains an indicated oxide copper resource of 3.21 billion pounds (511 million tons at 0.31% copper) and an additional inferred oxide copper resource of 0.88 billion pounds (159 million tons at 0.28% copper). For further details on the resource estimate, please see the news release dated July 19, 2011.

Hydrology Details

Two hydrological tests were completed on holes NSH-01 and NHS-02 and included pumping and injecting water to measure groundwater parameters, extensive down hole geophysical logging, geological logging and assaying, and advanced electrical geophysics. The two new tests complement previous testing in the late 1990's by Magma Copper Corporation (BHP-Billiton). The holes are all located in the central portion of the North Star Deposit as shown in the figure at: http://excelsiormining.com/Projects/GunnisonProject/Hydrology_Map.pdf.

Hydrological conductivities ("K values") are a measure of the efficiency with which water moves through the rock and are measured as feet per day (ft/d). NSH-01 had a K value of 0.08 ft/d measured over an interval of 394 feet (from 702 feet to 1,096 feet), representing the screened interval of the hole. NSH-02 had a K value of 5.9 ft/d measured over an interval of 656 feet (from 608 feet to 1,264 feet). The average K value for the two holes is approximately 2.9 ft/d. The K values achieved are entirely consistent with K values from similar ISR projects.

Excelsior's hydrological testing was supervised by Michael W. Bostic, R.G., Principal Hydrogeologist from BasinWells Associates, PLLC and a Qualified Person as defined by NI 43-101. Mr. Bostic has reviewed and is responsible for the technical information contained in this news release with respect to the hydrology details. 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 verified the data disclosed in this news release with respect to the resource estimate.

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 dated August 31, 2011.

ON BEHALF OF THE EXCELSIOR BOARD

Stephen Twyerould, President & CEO

Cautionary Note Regarding Forward-Looking Information

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 future exploration on and the development of the Gunnison Project and the ability to mine Gunnison using in-situ recovery mining techniques 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 the company 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.