Characterization of slate processing fines according to parameters of relevance for mine spoil reclamation

Slate processing fines (SPF) are mineral wastes produced during the preparation of roofing slate. Slate is extracted in open-cast quarries, that often result in disturbed sites and wastes that are thrown into dumps which are inhospitable to vegetation due to their poor water holding capacity and limited capability to supply nutrients. Covering the slate dumps with a layer of fine materials is expected to help reduce their adverse properties, thus facilitating a reclamation process. Revegetation success will depend on a number of factors such as the physical condition of the restructured soil, its nutrient content, the presence or absence of toxic materials and the selection of the plants best suited to the prevailing conditions. In this work the main physical, chemical and biological properties of the SPF have been determined, emphasizing those which will influence the successful establishment of vegetation. Since the electrical conductivity and pH of the SPF are in the range which is tolerable by plants, and the quantities of heavy metals are under the thresholds of toxicity, they could be used for this purpose but, due to the lack of nutrients and biological activity, and adverse physical condition, some organic amendment will be necessary for successful reclamation.