The possibility of producing ceramic powders suitable for the fabrication of microporous filters was investigated through the thermal treatment of the powder mixtures of a high-purity (99.09% SiO2) quartz and clinoptilolite type of natural zeolite. The quartz and zeolite, mixed in the ratio of 3:1 by weight, was wet ground in a ball mill, the powder was sieved on a 90-mum screen, and the undersize was dried and sintered in the powder form at the temperatures of 1000, 1100 and 1200degreesC for 7 h in an air furnace. The powder sinter products were deagglomerated by gentle crushing in an agate mortar and then characterized by phase composition, density, and specific surface area measurements. The added zeolite facilitated the transformation of quartz to cristobalite. The phase transformation of quartz to cristobalite first appeared at around 1000 degreesC, and, at 1200 degreesC, led to a ceramic powder sufficiently high in cristobalite content for the fabrication of the microporous ceramic bodies. Re-sintering at 1200 degreesC of the pressed forms of the ceramic powder resulted in microporous (0.5-3 mum) ceramics with a high porosity of 48.5%, and a three-point bend strength of similar to140 kg/cm(2). The ceramics obtained may have potential for filter applications. (C) 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.