All the ores so far we extract are almost the same except for a few.
Such as iron ore, copper ore and caterium ore have to go through a smelter to turn thet into ingots.So I thought it would be better to have different procedures to make ingots.
Such as in real life, aluminium is extracted by the process of electrolysis and I think it is possible to add that feature in the game.
Just use the coal to make carbon electrodes which needs to be continually replaced since it reacts with oxygen (or OH ions) to form CO2. And then the liquid aluminium can be sent to a cooler or something to turn them into ingots (not necessary as if the developers wish they can turn them to ingots in the electeolyele chamber but will be bigger and require more energy).
Also since the ore aluminium oxide has a high melting point, it maybe possible to mix it with other ores to reduce the melting point, also leading to having 3 inputs for the electrolysis chamber :coal, bauxite and another ore.
I hope this was helpful :)