Video and pictures: The neon blue lava flows of Indonesia's Kawah Ijen volcano

The sulphur mining industry in the Ijen volcano is dangerous work, but the sight of molten sulphur burning blue in the moonlight is extraordinary

Volcanic lava is a mesmerising sight at any time, but when these molton flows glow with a rich neon blue in the dead of night it’s even more captivating.

This phenomenon is the subject of a new project by photographer Olivier Grunewald who shot the video (above) detailing his trip to the active, but quiet Kawah Ijen volcano in Indonesia.

The volcano is topped by a 200-meter-deep lake of sulphuric acid and emits sulphurous gases constantly, with these fumes are tapped by local miners to harvest the chemical in its raw form.

The chemical undergoes a series of transformations throughout the process. It first condenses as a red liquid and when ignited by the worker’s torches it burns bright blue. Once it hardens it turns into a bright yellow solid.

The workers break up this with steel bars and then carry these heavy blocks to a local factory where the chemical is refined. A worker can earn up to 11 dollars a day in this way.

The mining operation is one of the major industries in the area, but it makes for dangerous work for the locals. The acidity of the water in the crater is high enough to dissolve clothing and cause breathing problems.

See below for a gallery detailing this extraordinary work