Analysis of 12 samples of Açungui phyllites showed rocks composed by sericite, kaolinite, quartz and goethite, without smectites and chlorites, and locally with sodiam zeolites. Their tones upon fire vary from white cream to dark brown and are directly related to Fe2O3 grades. The average grades are: SiO2 = 60.20%, Al2O3 = 22.33%, Fe2O3 = 6.27%, K2O = 3.84%, Na2O = 1.09% e TiO2 = 0.78%. S grades are <760 ppm, Zr <187 ppm, Nb <41 ppm, Y <29 ppm, As <18 ppm, Pb <33 ppm, Cu <39 ppm and Zn <47 ppm. After disaggregated, their granulation is 100% smaller than 0.04 mm, the average diameter of all particles is 8.42 µm, the average diameter of the smallest particle is 6.82 µm and of the largest is 13.20 µm. The a stretching values are > 165 cm x 10-7/ºC and they separate one group of phyllites with a < 205 cm x 10-7/ºC and another with a > 208 cm x 10-7/ºC. The average a value is 200.5. The final stretching average temperature is 833.7ºC. The average loss on ignition is 5.42%, of linear shrinkage at 1220ºC is -14.0%, of water absorption is 1.00%, of flexural strength before firing is 3.0 Kgf/cm² and is 80 Kgf/cm² after firing. There are two major phyllite types: (a) those with >0.8% Na2O, a greater than 208 cm x 10-7/ºC and with Na zeolites and, (b) those with <0.25% Na2O, a smaller than 205 cm x 10-7/ºC and without zeolites. The dark tones upon firing, high stretching and shrinkage index and low values of flexural strength after firing, confine the use of these rocks on ceramic compositions, pointing out to their use only as flux material.
phyllite; Açungui (PR, Brazil); chemistry, physical and ceramic properties
