Opals are formed when water and silicon dioxide ... Highlights: This is an extremely rare gem in the Taaffeite family, and until recently, only eight stones were known to exist.

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.

Opal is a gemstone of spectacular beauty and variety, enchanting connoisseurs and collectors with its kaleidoscopic play of colours. Revered as a symbol of good fortune and creativity, opal has ...