Parâmetros normativos das rochas ornamentais pegmatíticas do Seridó Oriental Paraibano - Pedra Lavrada/PB

Abstract

The rocks studied in the present work are known commercially as White Fuji, Capuccino Fuji and Golden Fuji. They come from the same mining front located in the municipality of Pedra Lavrada/PB. They have a similar mineral composition, consisting mainly of quartz, plagioclase, muscovite, microcline and garnet with modal composition between 5% and 34% and accessory minerals, with a modal composition of less than 5%, especially sericite, biotite and opaque. Petrographically correspond to pegmatites with isotropic structure, mineral granulation ranging from medium to very coarse, high degree of mineral microcracking, incipient to moderate mineral alteration and predominant concave-convex mineral contacts. The values obtained for the physical-mechanical properties indicate that the pegmatites investigated can be used as ornamental and coating rock, however, reservations regarding the use of the White Fuji pegmatite are required, as a function of their performance in the porosity, water absorption, uniaxial compressive strength and lexural strength exhibit values lower than the limits established by current standards. The results obtained in the radon exhalation of the studied rocks are considered high: White pegmatite (215,0 Bq/m3), Capuccino (176,3 Bq/m3) and Golden (156,0 Bq/m3). The results for radon gas exhalation eiciency demonstrate that the amount of 222Rn efectively emanated in the rocks is small relative to the total amount of 222Rn generated. The simulation for indoor environments shows that the dosimetric values obtained for White pegmatite were 0,88 pCi/L; 0,73 pCi/L for Cappuccino pegmatite and 0,64 pCi/L for Golden pegmatite revealing values below the dosimetric limit suggested by the United States Environmental Protection Agency.