A material is slaggable if it readily combines with fluxes at operating temperatures to form a molten liquid that separates from the heavier metal bath. Metallurgists analyze the mineral composition of ores to ensure the non-metallic portions are slaggable, preventing them from contaminating the final metal or freezing inside the furnace.
Heard on the job
The high alumina content makes this gangue barely slaggable unless we run the furnace much hotter.