I propose a "course of the horse", although, probably, it's already late. The furnace can be divided into three types (type) according to the principle of temperature:
- FIRST TYPE (type) stove "STONE OVEN (temperature up to 1100 degrees) would smelt the primary 5 metals, because according to their history there were 7 metals (still mercury and iron)
1. Gold
2. Silver
3. Tin
4. Copper
5. Lead
- SECOND TYPE (type) of the oven "OVEN WITH SMUMMER FURS" * (temperature up to 1600 degrees) would smelt only iron.
1) The furnace is made of stone, + wood, leather, copper, tin. (Justification: stone for the oven, leather for the furs themselves, wood for the designs of the bellows, tin and copper for the bronze rivets and clamps (I do not know if you will make alloys in the game, if not, rivets made of copper and tin) will spoil primary metals 3) Will not melt tungsten and other refractory metals - refractory metals will be shawls in a second type furnace.
- THE THIRD TYPE (type) of the furnace smelted refractory metals such as tungsten, for the production of which iron was required (cast iron, steel do not know your plans for metallurgy)
Add fines:
FIRST TYPE OF OVEN
1. Only the primary five metals melt
2. Does not melt any other metals
SECOND TYPE OF OVEN
1. Ignite primary 5 metals
2. melts iron
3. Does not melt refractory
THIRD TYPE OF OVEN
1. Destroys 1 5 primary metals
2. Ignite 2 iron
3. melts refractory metals.
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1 destroys: you can consider different options with the residual product.
2 Ignite: a variant in which two burnt ores are melted in a suitable furnace into one ingot of metal.
But, here, Aluminum in this scheme does not fit in any way, since it does not apply to the primary metals of mankind))))))))))))))
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* On the picture "blacksmith fur". I write in Russian and translate it from Google into an interpreter. The word Fur in Russian has two meanings, and the translator gives out: fur is a fox fur, mink, a bear in the plural, but it is necessary: a fur is a fan-shaped bubble for air in the singular.)))))