A blue miracle: How sapphires formed in volcanoes
Sapphires are among the most precious gems, yet they consist solely of chemically “contaminated” aluminum oxide, or corundum. Worldwide, these characteristically blue-colored crystals are mainly found in association with silicon-poor volcanic rocks. This connection is widely assumed to result from sapphires originating in deep crustal rocks and accidentally ending up on the Earth’s surface as … Read more
