Resource Upgrade Enhances Gunnison In-situ Copper Project

Press Release: MINING EXPLORATION UPDATE – 3 hours ago

VANCOUVER, BRITISH COLUMBIA--(Marketwire - March 4, 2013) - Excelsior Mining Corp. (TSX VENTURE:MIN)(EXMGF)(3XS.F) -

Highlights of Gunnison Oxide Resource Upgrade:

• 34% of metal in previous Indicated resource upgraded to Measured category
• Grade of Measured resource: 0.41% Cu
• Results based on 2012 drill program consisting of 10,502 ft (3,150 m) of diamond drilling
• New resource estimate uses cut-off grade of 0.1% total copper

Excelsior Mining Corp. (TSX VENTURE:MIN)(EXMGF)(3XS.F) ("Excelsior" or the "Company") is pleased to provide an update to its existing resource estimate for the North Star deposit, part of Excelsior's Gunnison Copper Project, located in southeastern Arizona.

Resource estimation: North Star copper oxide only at 0.1% total copper cut-off grade. This mineral resource estimate is effective as of March 1, 2013.

"By successfully moving a significant percentage of our Indicated resource to the measured category we have increased the geological certainty of the North Star deposit," stated Stephen Twyerould, President and CEO. "We are also very pleased with the consistency of this new resource calculation as compared to the previous calculation which garners confidence in the management team and the robustness of the deposit."

The previous mineral resource estimate of the oxide portion of North Star copper deposit consisted of an Indicated mineral resource of 511 M tons grading 0.31% for 3.21 billion pounds of contained copper metal, and an additional Inferred mineral resource of 159 M tons grading 0.28% for 0.88 billion pounds of contained copper metal.

The mineral resource estimate for the North Star deposit is based on results from 88 holes (129,272 feet) out of a total data base of 117 drill holes totalling 153,306 feet (ft) and is effective as of March 1, 2013. The resource estimation was performed by Independent Mining Consultants Inc. of Tucson, Arizona under the supervision of Dr. Roland Goodgame, VP Exploration and Director of Excelsior. Dr. Goodgame has reviewed and approved the technical information disclosed in this press release and is a Qualified Person (QP) as defined by National Instrument (NI) 43-101. Dr. Goodgame has verified the data underlying the results by supervising the drilling, sampling, assay, geology, quality assurance, quality control and interpretation. The estimate is classified as a Measured, Indicated or Inferred mineral resource, consistent with the CIM definitions referred to in NI 43-101. Excelsior is not aware of any environmental, permitting, legal, title, taxation, socio-political, marketing or other issues which may materially affect its estimate of mineral resources.

The mineral resource estimate is contained within a block model of the North Star deposit covering a surface area of 3.30 square miles and to a maximum depth of 2,575 feet below the topographic surface. The major geologic formations and oxidization types are incorporated into the block model based on the drill hole intercept data. The total copper grades are estimated using an ordinary kriging estimation technique from 25 ft drill hole composite data. The grade estimate for the sedimentary units uses a 700 ft circular by 50 ft search distance dipping 30 degrees east to parallel the general dip of the sedimentary units. The grade estimation respected the contacts of the various sedimentary units. The 700 ft distance is 70% of the variogram range. The total copper grades in the non-sedimentary units were estimated using a 500 ft spherical search. No copper grades are estimated in the overburden or un-mineralized rock units. Copper grade estimates based on eight or more holes are classified as Measured, grades based on three to seven holes are Indicated and grades based on less than three holes are Inferred.

All samples are prepared from manually split half-core sections on site in Arizona. Split drill core samples are then sent to Skyline Assayers & Laboratories in Tucson, Arizona for Total Copper and Sequential Copper analyses. Standards, blanks, and duplicate assays are included at regular intervals in each sample batch submitted from the field as part of an ongoing Quality Assurance/Quality Control Program.

Project Summary

The Gunnison Copper Project is located in a remote section of Cochise County in southeastern Arizona. The focus of the project is the North Star deposit, which currently has a total Measured and Indicated mineral resource of 3.21 billion pounds of oxide copper (498 M tons at 0.32%) and an Inferred mineral resource of 0.83 billion pounds of oxide copper (156 M tons at 0.27%). This oxide mineral resource has the potential to be mined using in-situ recovery methods. Mineral resources which are not mineral reserves do not have demonstrated economic viability.

About Excelsior

Excelsior is an exploration 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 its oxide copper resource has the potential to be mined using in-situ recovery methods. 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 Preliminary Economic Assessment, NI 43-101 Technical Report" dated November 18, 2011.

ON BEHALF OF THE EXCELSIOR BOARD

Stephen Twyerould, President & CEO

Cautionary Note Regarding Forward-Looking Information

This news release contains "forward-looking information" concerning anticipated developments and events that may occur in the future. Forward-looking information contained in this news release includes, but is not limited to, statements with respect to: (i) the estimation of measured, indicated and inferred mineral resources; and (ii) the ability to mine Gunnison using in-situ recovery mining techniques are forward-looking statements.

In certain cases, forward-looking information can be identified by the use of words such as "plans", "expects" or "does not expect", "is expected", "budget", "scheduled", "estimates", "forecasts", "intends", "anticipates" or "does not anticipate", or "believes", or variations of such words and phrases or state that certain actions, events or results "may", "could", "would", "might" or "will be taken", "occur" or "be achieved" suggesting future outcomes, or other expectations, beliefs, plans, objectives, assumptions, intentions or statements about future events or performance. Forward-looking information contained in this news release is based on certain factors and assumptions regarding, among other things, the estimation of mineral resources, the realization of resource estimates, copper and other metal prices, the timing and amount of future exploration and development expenditures, the estimation of initial and sustaining capital requirements, the estimation of labour and operating costs, the availability of necessary financing and materials to continue to explore and develop the Gunnison Project in the short and long-term, the progress of exploration and development activities, the receipt of necessary regulatory approvals, the completion of the environmental assessment process, the estimation of insurance coverage, and assumptions with respect to currency fluctuations, environmental risks, title disputes or claims, and other similar matters. While the Company considers these assumptions to be reasonable based on information currently available to it, they may prove to be incorrect.

Forward-looking information involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of the Company to be materially different from any future results, performance or achievements expressed or implied by the forward-looking information. Such factors include risks inherent in the exploration and development of mineral deposits, including risks relating to changes in project parameters as plans continue to be redefined including the possibility that mining operations may not commence at the Gunnison Project, risks relating to variations in mineral resources, grade or recovery rates resulting from current exploration and development activities, risks relating to the ability to access infrastructure, risks relating to changes in copper and other commodity prices and the worldwide demand for and supply of copper and related products, risks related to increased competition in the market for copper and related products and in the mining industry generally, risks related to current global financial conditions, uncertainties inherent in the estimation of mineral resources, access and supply risks, reliance on key personnel, operational risks inherent in the conduct of mining activities, including the risk of accidents, labour disputes, increases in capital and operating costs and the risk of delays or increased costs that might be encountered during the development process, regulatory risks, including risks relating to the acquisition of the necessary licenses and permits, financing, capitalization and liquidity risks, including the risk that the financing necessary to fund the exploration and development activities at the Gunnison Project may not be available on satisfactory terms, or at all, risks related to disputes concerning property titles and interest, environmental risks and the additional risks identified in the "Risk Factors" section of the Company's Annual Information Form for the most recently completed financial year or other reports and filings with applicable Canadian securities regulations.

Although the Company has attempted to identify important factors that could cause actual actions, events or results to differ materially from those described in forward-looking information, there may be other factors that cause actions, events or results not to be as anticipated, estimated or intended. Accordingly, readers should not place undue reliance on forward-looking information. The forward-looking information is made as of the date of this news release. Except as required by applicable securities laws, the Company does not undertake any obligation to publicly update or revise any forward-looking information.

Excelsior Mining Corp.
JJ Jennex
Vice President, Corporate Affairs
604-681-8030 x240
info@excelsiormining.com
www.excelsiormining.com