Gravel washing wastes from Jarama river deposits (Spain): an undervalued natural raw material

This work presents the main characteristics of 97 quarry wastes, collected in 23 gravel pits, from the Jarama river area, Madrid province, Spain. In this area, more than 2.5 × 10⁶ ton of silty-clay waste are generated every year, and no applications have as yet been defined for them. This work is the first systematic study of the fine fractions generated from the Jarama river quaternary deposits, playing part in the comprehension of this complex terrace systems. Quartz, potassium feldspar, plagioclase, calcite, and complex mixtures of phyllosilicates, such as smectite, illite, kaolinite, chlorite and illite/smectite mixed layer, have been detected. Two sets of waste which are recognized according to the calcite content, have been directly related with the terrace level beneficed in the Jarama river, and the position along the valley. Calcite concentrates in the wastes produced in the lower course, where Henares and Tajuña tributaries promote an extensive change in the geochemistry of underground water, and locally, in the petrology of quarried conglomerates. This clear distinction by location between calcite-bearing and calcite-free wastes is essential for potential applications, such as soil conditioning, raw materials for brick or tiles, etc. The wastes studied can be considered as a potential source of industrial raw materials because of their uniformity and large volume. This suggestion is now being carried out, with an attempt at assessing the possibilities of using these mining wastes as ceramic raw materials.