Mt Todd Gold Project - Gold Resource Update February 2009

Abstract

Tetra Tech, Inc. ('Tt') was commissioned by Vista Gold Corp. ('Vista') in September 2008 to prepare an update to the March 2008 Canadian National Instrument 43-101 (NI43-101) compliant Technical Report on the Mt Todd Gold Project (the 'Project') located in the Northern Territory, ('NT') Australia. On March 1, 2006, Vista purchased the Mt Todd property, and the acquisition was completed on June 16, 2006, when the mineral leases transferred to Vista and funds were released from escrow. An initial NI43-101 Technical Report was completed on June 26, 2006, a Preliminary Economic Assessment report was completed on December 29, 2007, an update to the resource report in March 2008, and this report is an update of the March 2008 Technical Report and is based on additional exploration drilling completed by Vista during 2008. The Mt Todd property contains a number of known occurrences of gold, which have been explored and/or exploited to various degrees. The largest and best-known deposits are the Batman and Quigleys Deposits. Both of these have had historic mining, with Batman having the most production and exploration completed. Currently, only the Batman Deposits has CIM compliant reported resources. At the present time, resources have only been estimated for the Batman Deposit. Tt created three-dimensional computerized geologic and grade models of the Batman Deposit. While the global model area also contains the Golf-Tollis and Quigleys Deposits, no geologic resource estimate has been made for these deposits at the present time. Tt used the geologic model that has evolved over the last few years, as adjusted by each exploration program, to guide the statistical and geostatistical analysis of the gold assay data. This model is a combination of lithologic and alteration data. The rock model was assigned a tonnage factor based on the oxidation state (i.e. oxidized, transition, primary). The tonnage factors are based on a number of tests from the core and, in Tt's opinion, are representative of the various rock units, and are acceptable for estimation of the in-place geologic resources. Estimation has been completed by using whole-block kriging techniques. This is the same estimation procedure as the previous Tt resource models, adjusted according to each successive drilling program. The estimation is completed as a 'two-pass' process. That is, the first pass is for the resources within the main core complex only using data from this zone. The second pass is for the material outside of the main core complex only using assays from outside the core complex. The estimated gold resources were classified into measured, indicated, and inferred categories. The classification was accomplished by a combination of kriging variance, number of points used in the estimate, and number of sectors used.