Sulfur

Sulfur (also spelled sulphur) is an element. Alternatively, the term brimstone also applies to sulfur, and was often used in the reference to Hell, in the terms of fire and brimstone. 

When combined with potassium nitrate and coal, sulfur can be used to create gunpowder. Native sulfur was found on the planet where James Kirk fought the Gorn captain in 2267. 

Kira Nerys told the Bajoran farmer Mullibok after supper in his cottage that he couldn't stay on Jerrado. Once the tapping started, the crust would release sulfur and carbon compounds that will make the air unbreathable. 

The sulfur lagoons of Hokath are a vacationing spot favored by the Voth. Similarly, the sulfur lagoons of Gorath are used as a test of endurance for Klingons on the Day of Honor. 

The The Doctor, after being transferred to the Alpha Quadrant to treat an uncooperative Lewis Zimmerman, suggested he would be off to visit explore sulfur mines if Zimmerman continued to object to being treated.