Aluminum

Aluminum is a metallic element, number 13 on the periodic table. Contrary to some popular belief, Aluminum and Tin are not the same material, Tin being atomic number 50. Aluminum is not found in a natural, pure form, rather in composite ores with many impurities, due to it's high natural reactivity. Therefore it must be extracted from these ores via a process called electrolysis, which was not invented untill 1800. it's presence in Castlevania: Curse of darkness is probably to express the talent of the alchemists of the time, like Hector, Issac, and others working for Dracula.

In gameplay, Aluminum is a fairly low grade material, but it has uses in several base level combinations for both weapons and armor, and concidering those items are used to create more and mroe advanced weapons and armor, it is adviseable to gather alot of these materials.