The Kawah Ijen Volcano is unlike any other volcano you have ever seen. Located in Indonesia, the mountain contains high levels of pure sulfur, which burns a bright blue-violet color when the volcano erupts.

The blue lava is extremely toxic, and reaches temperatures upwards of 239° F. Also, plumes of sulfur flames can rise up to 16 feet high.

But despite the grave risks, many local men make a living by trekking up the mountain to mine sulfur from the volcano’s crater, carrying it out by hand.

The miners’ average loads are usually between 180-200 lbs of sulfur. The sulfur they collect only sells for about 2.5 cents per pound, so most of the men make the trip twice every 24 hours.

Recently French photographer Olivier Grunewald traveled to the Kawah Ijen Volcano to capture the beautiful yet frightening spectacle. Check out more of his pictures below (click an image to enlarge):

Grunewald also recently teamed up with Régis Etienne, the president of Geneva’s Society of Volcanology, to produce a documentary on the mountain and the men who mine it. Watch the trailer below (the narration is in French but the images are still spectacular).