Transcript for On the Hunt for Rare Emeralds in Colombia
Deep underground -- the mountains of Colombia deeper and deeper from the -- for one of the world's most precious stone. -- about one football field wall for a green rock so yeah so valuable. These miners are willing to risk everything for a chance to find just -- -- -- That's the Jack -- -- -- me down a dark -- maze of -- huge steel gates meant to keep intruders out. Good work requiring strong arms. And even tougher nerves. -- -- last over -- so that's on the field. It's a wild frontier. Ruled by paramilitaries. Thieves and occasionally. Angry -- everybody's furious. They say that -- awaiting them but for those hardy enough to tough it out. Here's the prize this one's from that ideal world these are huge beautiful green -- -- -- could make them rich. Beyond their wildest dreams. Yeah. Our journey begins with a breathtaking flight over Colombia's lush fields of coffee and sugar. But the beauty is deceiving. Because many of those winding roads. -- ruled by guerrilla fighters. Everybody here is mean. Green fire an obsession he spent a lifetime chasing themselves. His name is -- -- -- he's one of Colombia's top Jim -- It's very rare for forty years he's tracked down the world's most expensive -- and wiser so much security there. Double locks on doors sometimes you can have a partial here that's -- of a lot of money. He's asking fifty pounds and he'll pay top dollar for private collectors and big museum. He's so well known in Bogota as -- district allows sellers -- -- hoping to catch design. He wants 500 for all of those England Connecticut they'll know. Out of it takes a special stoned to impress your. That's why he's agreed to take has directed the source. Northern Colombia's who's -- -- home to the richest and mineral deposits. Burned down there. Just call them my. Turf wars here in the 1980s left thousands dead. And while the violence is nothing like it was the threat of kidnapping and even murder is still very real. It was -- on the ground were greeted by the mine's manager he tells us we only have a few hours to explore. He can't guarantee our safety. Once the local gangs and militias find out -- here. We're going to a mine called me -- -- It's very isolated world is a land of desperation for so many people here is complete survival -- -- me tell you. People here -- will do anything to be able to get themselves. One way into the tunnels and and they will work. For no salary demands and to be a minor is hard. Hard I mean just a working on line is this it's horrendous. And there the lucky ones because some only get this far. Digging through the leftovers. -- -- not employed by the company they're allowed to do this whenever they find it very finisher with -- company. Won't find eventually. -- we find a more desperate scene. Women and even children sifting through scraps in the river mining company gives them these bags as a goodwill gesture. But it only stirs more resentment. If all these people been waiting since 2 o'clock this -- -- Not. Is and then as a name and you. It is -- read all of these people are just running down the -- they're only allowed to have one seed bags filled with the dirt that came out of the pits. Their dream is to go down wash it out with a water in the river. -- find some animals inside. They're still pouring through. Have you ever found an emerald in your life and -- -- Proof the best -- are still deep underground. So -- -- getting pushed out of here by the company that not happy there were even here they don't want us to really talk to these people anymore. They want us to get out and so we're gonna get out and as we suit up to go to the mines were given a safety briefing units that bit unsettling. -- -- -- We love you yeah yeah we -- This news. -- not a lot of -- -- guys are still. This is the oxygen we can green -- in an outbreak down. The bottom. -- then caught and -- horizontal. -- -- -- That noise is deafening but nothing compared to what I'm about. To experience. Will. I heard -- sound. About the most frightened residents and I was -- jackhammers going off so may they stop. And right behind the rock -- -- well where was left. Her that dynamite. Has allowed -- -- We meet -- 67 year old miner who has been working on these tunnels for forty years and how many animals do you think you found. Funeral but he's been able to survive what you tell your friends your children to -- have this job. You remember this is the last place that they found animals in the middle last year. For a year ago. There's only that they had been found animals down here since last -- keep a -- of words over a lot of them don't even mean you really is true kidding me. His guys -- there -- they just told us. Can one of their colleagues the ones work and on -- following -- gave it up -- just can't take it anymore and even when they do find emerald sometimes the company never finds out. They smuggle these while they've taken out of you know warm in the way it is and and the put him in the pocket sometimes and swallowing whenever you find some honesty put in your pocket and walk away -- The -- -- the guy in the blue helmet isn't laughing because he sent here by the mining company. To keep an eye on everyone to make sure we're not stealing. This -- from there I yhency ms. Seymour these are huge. But above ground proof. That even the best security measures don't always work all of these guys have been -- -- mining for the that a everybody here everybody here. How much to think all this is worth. -- -- may be around 5000 dollars you think that's about right now. -- -- that at that -- -- hope and where we're suckers and 5000 bucks for the non organizers -- you are much of credit. But our time is almost -- we need to get back to that helicopter before anyone gets its troubled -- -- -- -- beautiful valley and into. It's so we must leave this place empty handed. But as we fly over the hundreds of desperate prospectors still sifting in the river below. We get this reminder from the veteran of the -- For Nightline I'm Bob Woodruff.
This transcript has been automatically generated and may not be 100% accurate.