Sure they're eyesores, toxic hazards even. But mine dumps are true Jozi landmarks to orient by and now, for thrill-seeking adventure sport freaks, a playground. Powdery dunes made of mine tailings dot Johannesburg's skyline from Soweto through to City Deep and the East Rand. Many dumps get re-mined as gold prices spike and better technology makes it viable to sift through them one more time. But sand-boarders are interested in spikes and dips that have little to do with stock market whims and everything to do with making landlocked Johannesburg unexpectedly perfect for surfing.Phil du Plessis, a sand-boarding enthusiast and weekend instructor with Pure Rush Industries, said: "It's the only place you can ride dunes on an unmodified snowboard without having to wax the board, because the sand is so fine."For Du Plessis, a web developer by day, hiking up the dunes, strapping on his board and waiting for momentum and gravity to rush him to the foot of the mine dump is a perfect way to make weekends count.He said: "I grew up near Germiston. My parents used to say: 'Don't go near the mine dumps' and of course that's exactly where we went. And it's where we've returned to play as grown-up children."Pure Rush has been operating since 1994 and was started by extreme sport nut Marco Caromba. Caromba said once he and a few friends tried out the mine dunes for sand boarding they couldn't stay away and a business was born."People know it's a mine dump, we know there are risks, but it's Johannesburg - it's what Joburgers do," he said.Newbies join Pure Rush at "Mount Mayhem" in Benoni. It is a mine dump about 50m high, burns bright-white in the Highveld sun and has a gradient that looks angled way too steep when you have hiked near the top."Keep your knees bent, use your shoulders to steer and just keep your gaze fixed on where you want to be . and remember to let go of me too," Du Plessis instructs, as first-timers set their bodies and boards in motion.But virtually everyone gets sand-boarding right eventually and they don't need much encouragement to hike up again and again to the top. Monty Mathibi, a student and weekend instructor, adds: "If you're not falling you're not doing it right - just relax your body and roll it out if you wipe out." Mathibi has been riding for two-and-a-half years. He said: "I used to do skateboarding but I just love this."The rush is in the speed; the glide of the ride. It is tapping into the Jozi spirit that stares down your inner sissy and it is in surrendering to the beautiful tension of control and letting go, all contained in a few heartbeats...