I work in the steel industry so can provide some info here. In the mining of iron ore there is a step called "beneficiation" which involves the wet processing

I work in the steel industry so can provide some info here. In the mining of iron ore there is a step called "beneficiation" which involves the wet processing of minerals - this is not unique to iron ore and is common to many mining operations for a wide variety of materials, wet processing produces a waste slurry known as "tailings" which are typically stored in a dam or similar (https://en.wikipedia.org/wiki/Tailings_dam https://en.wikipedia.org/wiki/Tailings_dam) - tailings dams have been the cause of major environmental issues in the past. Such as the Brazilian Dam failure in 2019 which killed 250+ people. After beneficiation Iron ore is transported to a steelworks where it is smelted. The smelting process produces a further waste product "slag" (https://en.wikipedia.org/wiki/Slag https://en.wikipedia.org/wiki/Slag) how much slag is generated depends on a few factors such as the efficiency of the plant and the quality of the raw materials. Steelmaking slags can have some further use, for example it can be used in the concrete and cement industry and as a road base but how much if any of it is recycled very much depends on the country and the steelworks in some countries, particularly those with looser environmental restrictions slag is sent to landfill.