COOBER PEDY, AUSTRALIA - OCTOBER 22: Vistors walk through the underground tunnels in Tom's Working Opal Mine on October 22, 2015 in Coober Pedy, Australia. Tom's Working Opal Mine is an underground mine located within the active mining area, open to the public giving an insight into the workings of an opal mine. (Photo by Mark Kolbe/Getty Images)
