<p>Quarry dust is a waste material generated in rock quarries. Although its viability as a filler in concrete and virgin polymers has been demonstrated, limited information about its properties was found. In this study, quarry dust was sampled from three quarries near Nairobi. Based on XRD and XRF analyses, all specimens were identified as products of alkali basaltic rocks with the dominant minerals being rutile, analcime, nepheline and amphibole. Since no clay minerals were found in Mlolongo, it was identified as the best filler candidate. However, the biotite observed in Athi River and the smectite and kaolinite found in Kitengela will likely affect their ability to produce a reinforcing effect. All samples were generally coarse and would require grinding in applications where particle size is a crucial factor. Particle shape analyses by ImageJ showed that elongation decreased with increasing particle size. However, circularity and solidity increased with increasing particle size.</p> Graphical abstract <p></p>