Following is a transcript of the video. 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.

Black opal costs from $1,000 a carat to tens of thousands of dollars ... on the industry's color scale, which is more of a milk than a dark chocolate. More from So Expensive Meline: A pearl ...