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.

compared to common opal, which is usually one color. High-quality black opal can cost over $10,000 per carat, making it one of the world's most expensive gemstones. Over 90% of black opals come ...