Geological and Technological Aspects of the Piracaia Black Granite – SP

Abstract

The dimension stone named Piracaia Black Granite constitutes the commercial label of the fine to coarse inequigranular monzonites, locally with porphyritic fabric, and medium to dark gray colored from the Piracaia Massif. The rocks are homogeneous, but locally they are cut by quartz-feldspatic, quartzose or syenitic veins. A weak anisotropy is defined by a mylonitic NE-SW foliation with medium to high dip angle. The sets of fractures show preferred orientations around NNE-SSW/subvertical, E-W/subvertical, NW-SE/sub-vertical and subhorizontal, locally intense fractured close to fault zones. The physical and physical-mechanical, and the petrographic parameters of the Piracaia monzonites are close or ever better than the average values of the best “Brazilian Black Granites”, allowing to consider this rock as ideal to be used as a dimension stone both for internal and external environments. Homogeneity, dark color and weak alteration of the constituent minerals contribute to value the visual appearance and aesthetic pattern of the dimension stone.