In this study, the potential use of a natural raw material in the manufacture of blended cements was investigated. Mineralogical, petrographic and chemical analyses of the samples showed that the natural raw material was a porphyritic volcanic rock close to trachyandesite composition with a SiO(2)+Al(2)O(3)+Fe(2)O(3) content of 79.86%. Further experiments were also designed to determine the physical properties and pozzolanic activity of the raw material. The mortar samples, made with a binder of ground trachyandesite and lime, developed compressive and flexural strengths of 2.5 and 3.3 times respectively higher than those required for a natural pozzolan. Further tests revealed that when the ground trachyandesite replaced 30% w/w of Portland cement, the blended cements produced had the desired physical and chemical characteristics with compressive strengths higher than 32.9 N/mm(2). These findings suggest that this material can be used in the production of blended cements.