Cleopatra wore them. Elizabeth Taylor loved them. Egyptians believed they could bring eternal life.
Though diamonds enjoy the reputation of being a girl's best friend, emeralds in fact are more rare -- and more valuable.
"Sought after for their rich color, regal history and identifiable look, emeralds are one of the most iconic gemstones in the jewelry industry," Amanda Gizzi, a spokesperson for Jewelers of America, a New York-based trade association, said in an email.
On April 25, the public will have the opportunity to own some of the most magnificent and valuable emeralds in the world, when they go up for sale at Guernsey's auction house in New York.
With more than 20 cut and raw stones and 13 spectacular pieces of jewelry, the rare emeralds on offer all come from a single collection that was compiled by emerald specialist Manuel Marcial de Gomar throughout his long career in the emerald industry.
One of the highlights of the sale is a collection of cut emeralds from the great Spanish shipwreck Nuestra Señora de Atocha, a galleon that sank off the Florida coast in 1622.
The wreck is considered "the most valuable known shipwreck in history," according to the catalog accompanying the sale, largely thanks to its numerous Muzo emeralds, which are prized for their deep, clear green.
Trends in jewelry that see a rising popularity in colored stones have also made emeralds especially desirable in recent years. In fact, Gizzi predicted 2017 "will be a big year" for colored stones, including emeralds.
Members of the beryl family of minerals, emeralds obtain their rich green color through chromium, vanadium or iron deposits in the mines.
In the process, most stones form inclusions, tiny fractures or bubbles within their structure that can make them especially fragile.
While the best emeralds, like the best diamonds, are "clear," or inclusion-free, emerald connoisseurs generally also appreciate some inclusions, which they refer to as "jardins," French for "gardens."
Nevertheless, because the general buyer does tend to prefer clear stones, many commercial jewelers treat their emeralds to make the jardins less visible.
The gems of the Marcial de Gomar collection have not been subjected to such manipulations.
The loose emeralds -- some cut, others rough -- represent some of the best natural stones to emerge from the world's mines, according to Guernsey's.