Jewelry designer Nina Runsdorf was at a trade show in the early 2000s when a “large brown rock” the size of a pebble caught her eye. The seller told her it was a rough brown diamond. Runsdorf, in ...

The most valuable black opal features bright red stone against a very black base. In the '80s and '90s, gem-quality brown diamonds were worth about $1,500 per carat, but now many sell for up to $ ...

Mike says, 'Because nitrogen is so widespread, it is no surprise that pale tints of yellow and brown are the most common coloured diamond.' The colour is affected by how the nitrogen is scattered ...

The seller told her it was a rough brown diamond. Runsdorf ... Runsdorf bought it for $5,000, a steal for a stone of its size and quality. “It wasn’t considered precious,” she said.