The large, low grade, Kidston Gold Mine in North Queensland has
achieved outstanding economies of scale and profitability. The total
mineable ore reserve including mined to-date (as at December 1993) was
70.75 million tonnes at 1.54 grams gold per tonne. After nine years of mining, grade control mine production routinely
reconciles against mill production and ore reserves to within five per cent
of contained gold. The grade control system developed at Kidston is examined in detail,
with emphasis on the geological thinking behind the strategies, as well as
the development and application of a computerised, graphical production
control and reporting system. Reconciliation procedures and results are explained, illustrating the
success of geostatistical methods, as a risk management tool, in both ore
reserves and production grade control.