Because the grains of corundum are so small, less than 0.2 millimetres across, it was impossible to tell in images whether they are rubies or sapphires and what they might look like to the human eye.

“I would love to be able to pick one of those up and analyse it and see if it looks red – it’s pretty disappointing that all you can see is this white pebble,” said Ollila. But when hit with the SuperCam laser, they shone brightly.

Too small, unfortunately