A methodology for exploitation of ornamental slate deposits was develo
ped from data obtained from borehole exploration. The method begins wi
th the definition of geological, geotechnical and aesthetic parameters
that determine the quality of the slate deposit. Then a collection of
data from continuous sampling exploration was carried out in order to
propose a quality index through multivariate statistical techniques t
hat integrate all variables. This quality index is considered as a reg
ional variable and, by geostatistical methods, its value was extrapola
ted for each sample from surface exposures and boreholes. This allows
quantification of the quality of the deposit. (C) 1998 Elsevier Scienc
e B.V. All rights reserved.