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 ...

Here are some of the most incredible pieces of opal jewelry in honor of one of October’s birthstones. Oscar Heyman More emerald, 4.62 carats diamond, and 2.05 carats golden yellow diamond ...

A fine black opal that emits a wide spectrum of hues—from blue to purple to orange—and flashes of light is the most desirable and expensive opal variety.