Lightning Ridge is a small mining town outside of New South Wales, Australia renowned for its black opal, which can sell for over $10,000 per carat. But even for an expert miner, finding high-quality black opal isn’t easy. After investing tens of thousands of dollars, a miner might not find a single gem. But as soon as a gem quality black opal is found, opal cutters know they have a buyer for it. That exclusivity, and black opal’s unique colors, make it one of the most expensive gemstones in the world.