“‘Down there,’ said Golg, ‘I could show you real gold, real silver, real diamonds.’

“‘Bosh!’ said Jill rudely. ‘As if we didn't know that we're below the deepest mines even here.’

“‘Yes,’ said Golg. ‘I have heard of those little scratches in the crust that you Topdwellers call mines. But that's where you get dead gold, dead silver, dead gems. Down in Bism we have them alive and growing. There I'll pick you bunches of rubies that you can eat and squeeze you a cup full of diamond-juice. You won't care much about fingering the cold, dead treasures of your shallow mines after you have tasted the live ones of Bism.’”
— C.S.Lewis, “The Chronicles of Narnia: The Silver Chair”, Chapter 14, “The Bottom of the World”

This ornate spiral pattern came from the XaoS fractal zooming program, and I added the gold overlay and rubies. How any gems do you think there are?