Foreign Policy magazine has a very interesting photo essay on sulfur mining at the Indonesian volcano of Kawah Ijen, located on the eastern end of the island of Java.
The crater lake at the bottom of the caldera is so acidic that it can dissolve fingers and clothing. The sulfur is mined for use in cosmetics, gunpowder, and (surprise) anti-acne soap. The miners make a mere pittance of $0.05 for 1 kg (2.2 lbs.), which works out to about $11 per day. However, local farmers make only $1.65 per day, so the lure of "big money" is strong despite the many health problems miners suffer from. Those problems include bloodshot eyes, teeth eroded to stumps due to the acidic conditions, wheezing, allergies, sore stomachs, and damaged knees. Local people and agriculture have also suffered from the sulfuric pollution.
Be sure to view the rest of the photo essay as there are eight other pictures that are of interest.