Produced by oysters in oceans or mussels in rivers, pearls have been coveted by humans since the Bronze Age. So much so that it is believed the exploitation of freshwater pearls was a factor in the ...

The rarest of pearls include those which are naturally blue, pink, green, or purple. The most valuable pearls have high ...

Natural pearls are harder to find ... Black opal costs from $1,000 a carat to tens of thousands of dollars. The most valuable black opal features bright red stone against a very black base.

In the early twentieth century, a perfect pearl was considered the most valuable object in the world ... The wealthiest women in the world bought Cartier's pearls, but of all the well-known ...

In ancient Rome, pearls were more valuable than diamonds. Julius Caesar even passed a law saying only aristocrats were ...

A rare group of aligned, star-birthing dwarf galaxies resemble a cosmic string of pearls. Astronomers have discovered a rare ...

Astronomers have discovered a rare group of five dwarf galaxies located relatively close to Earth; these galaxies exist in a near-perfect alignment, resembling a string of cosmic pearls in the sky.