In the dual formalism of kriging, the estimation z_v is expressed as a linear combinaison of dual values C_∝ on sample points weighted by the mean covariances σ ̅ (v,a) plus an estimate of the trend m*. A new method involving an eigen value decomposition of the inverse kriging matrix is proposed to compute the estimation variance. The procedure avoids block kriging of the whole deposit. It is particularly adaptable to the kriging of irregular panels. The techniques have been tested or the “Minas de Leao” coal deposit (Brazil).