This work aims to study the possibility of producing lightweight aggregates from hazardous ornamental stone granitic waste in addition to clayey deposit. Six batch compositions were prepared in different proportions bracketed between zero and 50 % clay in the blank and 1:1 sample, respectively. The raw materials and the lightweight aggregates are characterized using XRD, XRF, DTA, transmitted light microscopy (TLM), cathodoluminescence (CL), X-ray micro-computed tomography (3D-μXCT) and SEM microscopy attached with EDAX. The results revealed that the contents of silica, alumina and total fluxes control the amount and viscosity of the liquid phase inside the aggregates during firing. The bloated aggregates show decrease in bulk density when the temperature and clay content increase. The microstructural and microchemical analyses show that a glassy phase is the major component in the lightweight aggregates. Some neogenic/remnant phases are randomly disseminated in the dominant glassy groundmass. The highly viscous melt, developed during firing, is the main reason for the small homogeneous pores in the blank sample. In contrast, the lower viscosity of the melt in the 1:1 sample is responsible for the existence of larger bubbles. All the prepared aggregates after firing at 1200 °C are lightweight aggregates which could be used in lightweight concrete as thermal and acoustic insulators.