The Hobbit

by J.R.R. Tolkien

was the Arkenstone, the Heart of the Mountain. So Bilbo guessed from Thorin’s description; but indeed there could not be two such gems, even in so marvellous a hoard, even in all the world. Ever as he climbed, the same white gleam had shone before him and drawn his feet towards it. Slowly it grew to a little globe of pallid light. Now as he came near, it was tinged with a flickering sparkle of many colours at the surface, reflected and splintered from the wavering light of his torch. At last he looked down upon it, and he caught his breath. The great jewel shone before his feet of its own inner light, and yet, cut and fashioned by the dwarves, who had dug it from the heart of the mountain long ago, it took all light that fell upon it and changed it into ten thousand sparks of white radiance shot with glints of the rainbow.