sulfur mine; sulphur mine
Refers to a mine where sulfur is extracted. The spelling 硫黄山 is straightforward and unambiguous.
Several old sulfur mines remain in this area.
Compound of 硫黄 (いおう, 'sulfur') and 山 (やま, 'mountain' or 'mine'). The reading いおう is the standard Japanese word for sulfur.