Right around this time last week I was over 1,000 feet underground at the Modder East gold mine, near Johannesburg, South Africa.
Actually, for as “cool” as the visit was, the mine was kind of warm.
After a couple hours walking — and at times crawling — underground, my T-shirt was soaked with sweat. I skipped the hotel gym that day.
The Modder East mine is one of the newest gold mines in South Africa. In May 2006, the site was a wheat field. By late 2009, the shafts were sunk, equipment was installed and operators pulled the first gold out of the ground. By mid-2010 the mine was cash-flow positive. Easy, right? No. Not at all. No way!
There are innumerable angles to this story. For now, I’ll just say that despite what I told you in the last paragraph, it’s hard — and I mean REALLY hard — to mine gold. You’ve got to see it to believe it. But then, that’s why we publish letters like this one — because if you can’t get out into the field, I’ll do it for you…
First, you suit up in safety clothing — Nomex overalls with lots of reflective patches and rubberized, steel-toed boots. Then you strap on about 25 pounds of other safety gear — headlamp, battery (one size — like a brick!), emergency breathing pack (one size — bulky) and more.
Suitably garbed in battle rattle, you go down an elevator shaft to the first level. The nonstop ride down takes you about as deep as the Empire State Building is high. At Modder East, you then travel through a long, dark, wet, rocky tunnel about 12 feet wide by 15 feet high — the main adit.
Eventually, you get to what are called “side panels,” where eight-men (and a few women) teams of miners chase “gold reefs” far into the crust of the earth. Using water-powered tools, they drill holes into the rock. Then a guy called the “blaster” comes along and emplaces charges. Twice a day, the earth shakes with energy from explosions.
After blasting is over, a few brave souls go in to check rock stability. Later, after the all-clear signal, miners move in to haul out the debris. At Modder East, the pay zone is called the “Buckshot Reef.” It’s a quartz pebble conglomerate heavily infused with gold-laced pyrite (and yes, of course, I have a sample).
Look at the photo above. Now consider that the Buckshot Reef ore zone is about 8-12 inches thick, at best. Sure, it’s rich in gold — around 40 grams per tonne. But you can’t just mine a 1-foot seam. There’s no technology for that.
You have to remove a lot of rock — mostly below the ore zone, just to get the pay dirt out. But you can’t dig out too much barren rock, because you’re paying for every hunk that you break up and move out. It’s all about cost per tonne.
Thus, this kind of mining involves digging relatively thin “panels” out from the side of the large main tunnel. How thick are the side panels? Well, just to get things started, there’s a very tight, perpendicular, man-sized hole where the driller stands.
This more or less perpendicular hole strikes out from the main tunnel. And off that hole, miners dig out into the ore zone, creating an opening about 4 feet high. All along, the miners have to support the roof with thick timbers.
During the mining and clearing process, large chunks of Buckshot ore (gold-infused pyrite) go straight into the mine carts, to be hauled to the surface. But after that, there’s a lot of fine detritus as well — it’s the remnant debris of the blasting-mining process.