Soon after this rebranding, Chocolate Diamonds took off ... making it one of the world's most expensive gemstones. Over 90% of black opals come from Australia, but they aren't easy to find.

Also, check out the most expensive pieces of jewelry. Earning passive income doesn't need to be difficult. You can start this week. The Graff Pink, a 24.78-carat fancy intense pink diamond ...

Read Next: I’m a Financial Advisor: My Wealthiest Clients All Do These 3 Things Find Out: 12 SUVs With the Most Reliable Engines Here’s a look at the most expensive diamonds ever purchased and their ...