Black opal costs from $1,000 a carat to tens of thousands ... In the '80s and '90s, gem-quality brown diamonds were worth about $1,500 per carat, but now many sell for up to $10,000 per carat.

There is less soil being moved. We have a less carbon footprint," said Good. Good said lab-grown diamonds tend to cost about 30 to 40 percent less than mined diamonds of the same carat ...

The 555.55 carat black diamond has belonged to its current owner for two decades but little is known about its history before that. A billion-year-old black diamond, believed to be the largest cut ...

"We just looked at diamonds and we didn't think about costs or how these particles could be mined," he said. "But obviously these are also questions that need to be considered [to determine] if it ...