Maybe implement more metals and their refining processes.

With copper, iron, gold and uranium we have some of the more important elements/minerals in the game.
I think it would be cool to have more elements, their naturally occurring minerals and processes for purification tho.
E.g.: Aluminium
Aluminium is mined as "Bauxite" which contains iron as well and therfor could give both in the process. To process it with the Bayer-process, we need caustic soda. To get caustic soda the chloralkali-process needs to be implemented. To finally get the pure aluminium we will need a fusion electrolysis like copper.

There are a lot of possible elements to implement and I think it would be fun to see some more ores and espacially the processes to get the pure elements.
(Graphic used for reference which metalls are mined/refined the moste and could be added)