A Mine, Mine
noun
A mineral mountain is one that you should build a mine in, to get all those minerals.
こうざん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own. Watch out for the rendaku.
鉱山で働いてる時は、いつも背中に痛みがありました。
When I worked in a mine, I always had back pain.