Warnings against the use of limestone as an aggregateAggregates in potline basement concrete were first highlighted in 1987 after Comalco’s Boyne Island SmeltersSmelter observed that metal spilled onto the basement floor from pot tap-outs were initiating thermiteThermite type reactions. DolomiteDolomite is a common mineral that also finds use as an aggregateAggregates in concrete. Being a carbonate-based mineral, it carries a similar risk as limestone for initiating a thermiteThermite reaction with molten aluminumAluminum. Due to this risk, the use of dolomiteDolomite as an aggregateAggregates material should also be prohibited in molten metalMolten metal areas. For smeltersSmelter that do not have detailed records of the aggregateAggregates used in their concrete, a simple sampling and analysis procedure can be used to identify the type of aggregateAggregates present. If dolomiteDolomite or other carbonate-based materials are found, reaction plans should be developed to mitigate the risk that they pose.