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.