. >> the salar de uyuni is visible from outer space.his salt flat -- the world's largest -- sits 3700 meters above sea level. people have harvested salt here for hundreds of years. just like his ancestors, elias leaves his house early in the morning and makes his way to the white desert. >> working in the salt fields is hard. i've been doing this since i was 5 or 6 years old. >> and it's back-breaking work -- nearly entirely done by hand. you have to break through the hard upper crust with a pike until you can see water. then you stack the salt into mounds in order to dry it. to fill a truck, you have to move 10- to 12-thousand shovels full of salt. >> but this era could soon be coming to a close. the real treasure under elias' feet isn't salt but rather lithium. the light metal is the most important raw material that goes into making heavy duty batteries. this element could make bolivia rich. salar de uyuni contains the world's largest lithium reserves. the price for this silvery- white metal -- already up 400% over the past few years