The movie, starring Leonardo DiCaprio, portrays the corrupt gem-dealing that financed the 1990s civil war in Sierra Leone. Many diamond merchants were worried the film would hurt sales, but retailers say the opposite is happening: Diamond purchases are booming.

The demise of the "dirty diamond" trade is thanks to two things. The first was the 2002 Kimberley Process, which requires diamond companies worldwide to register the origin of their gems. "According to the World Diamond Council, this has shut out 99 per cent of the illicit diamond trade," says Reuben Tom Kee, creative director for Jubilee Fine Jewellers and Canadian diamond company Polar Bear Diamonds.

The second is the growing popularity of diamonds from Canada. Polar Bear diamonds, for example, are mined and cut in the Northwest Territories, and each one comes with a certificate of origin.

"The Canadian diamond industry is less than eight years old and has now climbed to the third-largest producer of diamonds in the world," says Tom Kee. He suggests one way to feel confident about the origin of any diamond you buy is to ask to see the certificate of origin.

TRADITIONAL CUTS ARE STILL TOPS

As with fashion, Hollywood's elite is often the biggest influence on engagement-ring styles, and some rings are almost as famous as their wearers. There is the Edwardian-style setting that Tom Cruise gave Katie Holmes, Heidi Klum's canary yellow diamond, an oval shape sported by Nicole Kidman, and Eva Longoria's new five-carat emerald-cut ring from Tony Parker.

"Celebrity weddings definitely fuel the curiosity level, but the fancy cuts are not necessarily the ones that new couples would buy," says Tom Kee. "They tend to lean toward the traditional and more recognizable shapes. Round brilliant and princess (square)-cuts are our top-selling shapes."

He says only one in 50 customers asks for a fancy cut such as a marquise, oval, emerald, heart or pear.

OUT OF THE ORDINARY

Romancing the stone 
Katie Holmes sports the Edwardian-style ring given to her by Tom Cruise.

Diamonds come in a rainbow of colours, and ever since Jennifer Lopez received a mammoth six-carat pink diamond from then-fiance Ben Affleck, coloured diamonds have been catching the attention of young couples. However, since they are more rare than white diamonds, these colourful rocks are -- sometimes prohibitively -- more expensive.

"Right now, yellow diamonds are attracting a lot of attention," says Tom Kee. "The yellows are more accessible than the reds and pinks." He says a coloured diamond is ideal for someone who wants something different and unusual.

If you want the look of an instant heirloom, keep your eye out for an estate ring, suggests gemologist Stephanie Appotive. Older diamond jewelry offers beautiful craftsmanship and often one-of-a-kind design.

Appotive is also seeing rings with a centre diamond flanked by coloured gemstones, and says some couples have requested gemstones in their wedding bands.

She suggests couples go with their gut instead. "Look at the diamond and make sure it looks beautiful to you. You have to find something you really love, because this is forever."