The effect of boron addition on basalt and basalt-dolomite mixtures was tested for rock wool production. The melting temperatures and the viscosities of the melts were determined and SEM and EDS analysis on some samples were done to find out the effect of boron addition. It was observed that boron addition lowered the melting temperatures noticeably, slight increases in the viscosities were at acceptable levels and no negative structural changes were caused. It was concluded that boron could be added for the rock wool production and the quantity to be used could be adjusted considering the melting temperature and the viscosity value. (C) 2020 Elsevier Ltd. All rights reserved.