The Volcano That Burns Blue

Koala Jen volcano in Java, Indonesia, features a highly acidic Crater Lake and emits rare blue flames at night due to sulphuric gas combustion. The cooled gas forms yellow sulphur, which is mined despite the toxic and dangerous conditions. The volcano is both a challenging workplace and a unique natural wonder.

What is mined from the Koala Jen volcano and how is it used?

Why is the work of miners at the Koala Jen volcano considered dangerous?