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.

Once rough opal is extracted and processed from the dirt, it has to be cut and polished. This is when the real value of the gem is determined. There's a huge demand for black opal, with lack of ...