They're also one of the most expensive nuts in the world, selling for upwards of $117 per kilogram. So what makes them so special? And why are they so expensive? More from Retail Pine nuts have ...

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.

Every year, wealthy multi-million or billionaires camp at different auction houses to bid on the most valuable items in the world ... which is why the most expensive item ever to be sold at ...