No matter the reason for their price, here are the 35 most valuable gemstones in the world, ranked by their price per carat weight. And, yes, this list does include diamonds, emeralds, rubies and ...

Narrator: High-quality black opal can cost over $10,000 per carat, making it one of the world's most expensive gemstones. But mining black opal isn't easy. After investing tens of thousands of ...