(IDEX Online) - An extremely rare type of diamond has been discovered in Australia - but it will be of more interest to geologists than the gem industry.The "metamorphic diamonds" are invisible to the naked eye and can only be viewed with a laser and a microscope.Researchers from James Cook University, in Queensland, found them in rocks along the Clarke River Fault, west of Paluma in the north of the state, according to Science Advances Journal."We had to analyse many, many thin sections of rock, and to prove the diamonds were there, it took about a year-and-a-half," said Dr Ioan Sanislav, from the university.Metamorphic diamonds are only known to exist in six other locations in the world. In some cases they are so small they can't even be seen with a microscope.They are formed from the massive increase in pressure and temperature when land masses collide.Although they're of no use to the diamond industry, they may provide valuable information about the tectonic movements that formed Australia.Pic courtesy James Cook University