Physical characterization of an extensive volcanic rock in México: "red tezontle" from Cerro de la Cruz, in Tlahuelilpan, Hidalgo Caracterización física de una roca volcánica abundante en México: "tezontle rojo" proveniente del Cerro de la Cruz, en Tlahuelilpan, Hidalgo

Tezontle is an extrusive volcanic rock, coming in black or red in color. Despite its many uses and applications, there are few studies concerning the attributes of this rock. Therefore, this work to the physical characterization of red tezontle samples, taken from Tlahuelilpan, Hidalgo, Mexico. After grinding and sieving, the following properties were obtained: humidity (0.37% to 0.48%), weighed moisture-retention capacity (7.50% – 43.56%) and volumetric moisture-retention capacity (5% – 25%), which justifies its hydroponic and gardening uses; particle density (2.37 g cm -3 - 2.83 g cm -3 ), dry bulk density (0.87 g cm -3 - 1.33 g cm -3 ), total pore space (52.83% - 63.90 %), specific surface area (5.558 m 2 g -1 and 9.66 m 2 g -1 ) and cation exchange capacity (4.04 Cmol(+) kg -1 ), whose low values contradict the high efficiency reported for cation removal. The preliminary analysis of the X-ray diffraction pattern shows intense peaks of quartz and suggests the presence of plagioclases (anorthite and albite). RESUMEN El tezontle es una roca volcanica extrusiva y de coloracion negra o rojiza. A pesar de sus multiples usos y aplicaciones, existen pocos estudios respecto a sus atributos. Por ello, el objetivo de este trabajo consiste en la caracterizacion de muestras de tezontle rojo provenientes de Tlahuelilpan, Hidalgo, Mexico. Despues de molido y tamizado se determinaron las propiedades: (0.37% - 0.48%), grado de hidratacion (7.50% – 43.56%), hinchamiento (5% – 25%), que justifican su aplicacion en hidroponia y jardineria; densidad real (2.37 g cm -3 - 2.83 g cm -3