Illegal gold mining has plagued South Africa's mining companies for decades, robbing the industry and state coffers of billions of rand through small-time pilfering as well as networks run by organised crime.
Now, with unmined output dwindling and proving more difficult to extract, one has had enough: diversified precious metals producer Sibanye Gold says that it will clear all illegal miners from its shafts by the end of January next year.
Masimthembe used to be the gateway to other shafts at nearby operations through a network of linked tunnels.
Now Sibanye says it has been effectively cleared of "Zama Zamas" - the Zulu term for illegal miners, meaning "taking a chance".
To gain access to elevator cages going down to Sibanye's mine, visitors must negotiate a series of high-tech turnstiles which require a biometric reading of your index fingers and can trap you if you are not authorised to pass.
"Because we are deep level mines, and currently mining up to 3 kilometers below ground; we are fortunate in a sense that… when I say fortunate, I use it loosely. Illegal miners can only get to our underground workings through conveyance - which is the cages that we call it in. It's the manned conveyance that travels from the surface to up to 3 kilometers and beyond, below. So access control is probably very key here," said Nash Lutchman, Sibanye's head of security.
Illegal gold mining costs South Africa's government and industry more than $1.5 bn a year in lost sales, taxes and royalties, the Chamber of Mines estimated in an unpublished document submitted to parliament in March.
The challenge to end illegal mining is immense.
Sibanye may win most of the battles but it will lose the war in a country beset by joblessness, poverty, crime and porous borders, experts say.
Most zamas are undocumented immigrants from neighbouring countries that have long provided migrant labour for South Africa's mines who are now being laid off.
The syndicates who support them and traffic the illegal metals are well-funded, well-established and highly dangerous, security experts say.
The zamas can spend weeks underground, supported by criminal networks who provide tools, food and water.
Inside the mines, Sibanye security workers showed a Reuters reporting team the kind of spot favoured by illegal miners, an area where ore blasted in legal mining operations has been scraped away from the rockface.
Stop the practice
There, zamas wash rocks that have been left behind over a metal plate wrapped in carpet.
The gold-bearing material gets caught in the carpet, which is then washed out in a bucket of water.
After mercury is added, presto: a nugget that may be 50% gold.
Sibanye's strategy for eradicating the problem also includes a tip-off and reward system to encourage employees to report suspicious activity, tactical security units that can go underground to make arrests, along with the access checks to ensure only authorised personnel gain entry.
"So what was happening in the past is that illegal miners were being facilitated into our mine by an employee, so we call that 'piggybacking'. Now I would for example use my access control card to get the turnstile open and then once it opens, I would squeeze somebody's self inside the turnstile with myself - that's called 'piggybacking'. So the turnstile design together with your biometric fingerprint access control and your cards and other controls around access control was the point of departure to try and keep the unauthorized people out of it," said Lutchman.
A Gold Fields spin-off formed in 2013, Sibanye is the first company to set itself a deadline to stop the practice and has laid out $15m to make it happen.