When thieves staged a $50 million diamond heist at the Brussels Airport earlier this week, the theft made international headlines not just because of the value of the stolen gems, but because diamonds hold so much worldwide allure and romanticism.

“You mention the word ‘diamond’ and it takes on a whole new level of interest,” said Jeff Post, curator of the national gems and minerals collection for the Smithsonian. “That’s why we have the Hope Diamond in front of our exhibition hall. It’s like going to the Louvre and making sure you go see the Mona Lisa first.”

Why do we have such a love affair with diamonds? Science and history explain some of the attraction.

PHOTOS: World's Rarest Gemstones

“There are a lot of superlatives about diamonds that separate them from everything else on earth,” Post said. “They’re the hardest things known, the best conductor of heat...they’re obviously a special kind of substance. But I think the real miracle about every diamond is that it had to be this crystal that was almost perfectly formed 100 miles below the surface of the Earth, and survived essentially a violent rapid volcanic eruption to bring it to the Earth’s surface and then found or mined.”

Combine that chaotic trip through the depths of the Earth with the fact that most diamonds are 1-3 billion years old and the cultural value of the diamond begins to make sense. Diamonds have been known and valued for at least 3,000 years; there are ancient Greek accounts of Alexander the Great’s soldiers searching for diamonds in India in about 326 B.C.

“Diamonds were mined and traded when we were still basically living in the Dark Ages,” said Russell Shor, senior industry analyst at the Gemological Institute of America. “When the ancients saw these crystals that could basically cut anything, they must have been truly amazed.”

BLOG: Diamonds Journey to the Center of the Earth

People have always recognized diamonds as something of great value, worth more per volume than almost anything else, Post said. And because diamonds used to be much rarer than they are now, they were owned almost exclusively by the wealthy and powerful, who passed them on from generation to generation.

“The first recorded diamond engagement ring was when Archduke Maximilian of Austria proposed marriage to Mary of Burgundy in 1477,” said Ruth Batson, CEO of the American Gem Society and AGS Laboratories.

“At the time, diamonds were a rarity and were reserved for royalty and the upper elite class. Over time, it was adopted by the other classes, and became a Western tradition.”

Why do we love diamonds so much?Corbis

One of the first questions people ask when they visit the collection at the Smithsonian is who the previous owners of the gems were.

“It ties us to the people who might have owned it in the past, and the stone becomes more than just a stone -- it’s a connection,” Post said.

Today, synthetic diamonds rival natural ones in terms of looks; jewelers offer them as a cost-effective alternative, especially the colored versions, where the cost difference can be in the tens of thousands of dollars.

NEWS: This Diamond Planet Will Last Forever

“For people who just want the bling and to be able to say, I have a big flashy diamond that’s bigger than yours, synthetic diamonds will fulfill that need just fine,” Post said.

Because they are grown under controlled conditions, laboratory-grown diamonds can have high color and clarity like naturally-formed gem diamonds, Batson said, “and are often used in technological applications where high purity is required.”

While the optical properties of natural and synthetic diamonds are identical, she said, bits of other minerals, called inclusions, are sometimes found in natural diamonds -- and are not reproduced in a lab.

But some people will always want that romanticism of knowing the gem on their finger came from the Earth, experts said. The origin of natural diamonds, experts agree, lend the diamond both their value and lure.

“It gives diamonds a certain cache, a prestige we really can’t fight,” Post said.