Mineral
Aside from gold there are a wide variety of other minerals as well.
Think of the wide range of minerals there are that aren't gold. There are a lot.
こう
あらがね
None
One person is trying to control all the minerals of the world. That person is Emperor こういち.
Emperor こういち is getting all the minerals, and the 鋼, so he can take over all neighboring nations and force them into a subjugation of efficient kanji learning.