Rio Alto Mining Limited
TSX VENTURE : RIO
FRANKFURT : MS2
BVLAC : RIO

Rio Alto Mining Limited

April 08, 2010 09:01 ET

Rio Alto Announces Early Completion of Metallurgical Tests

CALGARY, ALBERTA--(Marketwire - April 8, 2010) - Rio Alto Mining Limited ("Rio Alto") (TSX VENTURE:RIO)(BVLAC:RIO)(DBFrankfurt:MS2) is pleased to announce that the series of metallurgical tests undertaken by Heap Leaching Consulting S.A.C. ("HLC") of Lima, Peru on a 100 tonne sample of representative material from Rio Alto's La Arena Gold Oxide Project has been completed several weeks in advance of the previously anticipated completion timeline of late April or early May. HLC has advised Rio Alto that the run-of-mine column leach test work was completed several weeks sooner than anticipated due to favourable leaching characteristics of the sample material. Rio Alto anticipates receiving the report from HLC regarding the result of these metallurgical tests in mid-April.

Rio Alto, in consultation with Coffey Mining Pty. Ltd. ("Coffey Mining"), determined to defer the completion of an updated reserve estimate and associated NI 43-101 Technical Report (the "Report") on La Arena Project so that the results of these metallurgical tests can be independently verified by Coffey Mining and incorporated into the reserve estimate for the La Arena Gold Oxide Project to be presented in the Report. Coffey Mining is scheduled to undertake its verification process in mid-April 2010 with the Report anticipated to be completed in May 2010.

Rio Alto announced, on August 5, 2009, that it had engaged HLC to conduct tests to determine the gold recovery cycle and processing costs for the purpose of determining the design specifications for a gold recovery plant for La Arena Gold Oxide Project. Management of Rio Alto anticipates that favourable leaching characteristics of material taken from La Arena Gold Oxide Project will, during the initial years of the project, result in a higher gold recovery rate, a shorter gold leach cycle and lower processing costs as compared to earlier estimates.

Rio Alto will announce the results of these metallurgical tests once independently verified by Coffey Mining.

Forward Looking Statements

This news release contains certain forward-looking information including statements concerning the leaching characteristics of material taken from La Arena Gold Oxide Project, the metallurgical test results, the expected timing of the availability of independently verified metallurgical test results, the preparation of a NI 43-101 Technical Report on La Arena Gold Oxide Project and the length of the gold recovery cycle and processing costs of a mine that may be constructed on La Arena Gold Oxide Project. All statements included herein, other than statements of historical fact, are forward-looking information and such information involves various risks and uncertainties. There can be no assurance that such information will prove to be accurate, and actual results and future events could differ materially from those anticipated in such information. A description of assumptions used to develop such forward-looking information and a description of risk factors that may cause actual results to differ materially from forward-looking information can be found in Rio Alto's disclosure documents on the SEDAR website at www.sedar.com. Rio Alto does not undertake to update any forward-looking information except in accordance with applicable securities laws.

To learn more about Rio Alto Mining Limited, please visit: www.rioaltomining.com

ON BEHALF OF THE BOARD OF RIO ALTO MINING LIMITED

Alex Black, Chief Operating Officer

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

Contact Information