New York ? The Diamond Information Center says “a diamond is forever.” The promotional phrase is pretty darn close to the truth.

The slogan, used in public relations and advertising campaigns, borrows heavily from the beliefs of ancient societies.

A diamond was used as a symbol of love and passion by ancient Greeks and the gemstone — albeit in its uncut, octahedron shape — married the ring as an emblem of betrothal during the third century when the Romans ruled, says Joyce Jonas, president emeritus of the American Society of Jewelry Historians. However, instead of giving the ring to the bride at the time of engagement, it was given to her at the wedding.

Nowadays, one out of every three jewelry purchases is made by a bride or groom, according to Conde Nast Bridal Infobank. Engagement ring sales total $6 billion annually.

“Most women still want a diamond. It’s the stone of choice for brides. They’re beautiful, precious, timeless, lasting and traditional,” says Millie Martini Bratten, editor in chief of Bride’s magazine.

Romance and rocks

Even the word shines with significance: The Greek word for diamond is “adamas,” strikingly similar to the Latin verb “adamare,” which means to love passionately. The French word “aimant” means loving.

A new exhibition, called Diamonds & the Power of Love, sponsored by the Diamond Information Center, traces the close relationship between romance and rocks. The exhibit includes new one-of-a-kind diamond designs from Bulgari, Chaumet, Van Cleef & Arpels, and Escada, among others, as well as historical rings, including a reproduction of the first-known engagement ring that Archduke Maximilian of Austria gave Mary of Burgundy in the 15th century.

Diamonds & the Power of Love opens Valentine’s Day and runs through Feb. 23 at the Ritz-Carlton in Henderson, Nev., before moving this summer to the Place Vendome in Paris.

During ancient times, jewelry was exchanged as a way to ask the gods to give something to the recipient, says Jonas, who also is the director of the trade conference Jewelry 2003. For instance, a gift of rubies was a request to cure an ulcer; corals were supposed to fend off evil spirits.

Bonds with each other

This Tiffany-style setting with a solitary brilliant-cut diamond suspended above two baguette diamond shoulders is from the 19th century. It is part of Diamonds & the Power of Love, an exhibit sponsored by the Diamond Information Center.

Diamonds were known as the gift of unconquerable love because they are so durable. The stone’s color never changes. It never breaks. It doesn’t even melt.

“People want that in their bonds with each other,” Jonas says.

She adds, “Diamonds have always been the most revered stone. A ring is seen as the everlasting eternity of a relationship. … And it all comes together in a diamond ring.”

Even with changing trends and tastes, the diamond ring has remained the favorite engagement ring. And for as long as the diamond ring has been coveted, it’s also been used as a status symbol.

According to Jonas, there are several paintings from the 15th century that depict kneeling young men holding diamond rings. The paintings would be sent to the men’s arranged brides-to-be as an introduction.

“The painting could say ‘I’m a wealthy or successful man’ based on the ring size. It becomes a status symbol that says, ‘Look at the ring I can give you,”‘ Jonas explains.

Victorian Era

Diamonds, worn only by royalty until the 15th century and expanding to the wardrobe of the gentry class for the next couple of hundred years, became more readily available for the masses in the 18th century after Indian diamond mines were discovered.

“The 18th century was the Age of Diamonds,” Jonas says. “All fashionable women wore as many as she could.”

During the Victorian Era, she notes, women began to wear a new, more affordable look, the three-stone ring, in which a small diamond was surrounded by two other gems, such as a ruby (for passion) or a sapphire (for eternity).

Solitaire and brilliant-cut diamonds were all the rage during the mid-20th century. Currently, brides favor fancy shapes, such as teardrops and marquis turned on their sides, or vintage and antique styles that have the benefit of 21st-century technology, reports Bratten.

Until recently, diamonds traditionally had 58 facets to help the stone catch light, but now there is the Leo Diamond with 66 facets and the Criss Cut with 77.

“Jewelers are always looking for ways to maximize the sparkle of the diamond,” Bratten says.

But, she adds, the biggest change in diamond engagement rings has been the manner in which they’re chosen.

For generations the man was expected to choose the ring and present it — along with his proposal — as a surprise. Now it’s very common for a woman to at least suggest some styles if not go with him to do the shopping.