Harry Winston Diamond Corp. has signed a deal to sell its namesake retail jewelry and watch division in a deal valued at $1 billion US in cash and assumed debt to Switzerland's Swatch Group.

The Toronto-based diamond miner will be renamed Dominion Diamond Corp. after the deal closes.

"At the time that we purchased the Harry Winston brand, resource investment opportunities for diamonds were rare and expensive following the euphoria of the Canadian diamond discoveries, and the involvement of the large international mining companies," said Robert Gannicott, Harry Winston's chief executive.

"Today there is a range of diamond resource opportunities while the value of heritage luxury brands has increased dramatically. This transaction represents a sound return on our original investment."

Gannicott said the company's mining business will be well-equipped "in an environment where cash has become a strategic resource while preserving and expanding our relationship with the downstream diamond business."

Swatch will pay Harry Winston $750 million and assume $250 million in debt owed by Harry Winston.

The Harry Winston brand is named for a celebrity jeweller, mentioned in the enduring song "Diamonds Are a Girl's Best Friend" from the 1953 musical Gentlemen Prefer Blondes.

Swatch said Harry Winston will complement the prestige segment of the Swiss group, which is one of the world's biggest makers of watches.

"We are proud and happy to welcome Harry Winston to the Swatch Group family — diamonds are still a girl's best friend," said Swatch chairwoman Nayla Hayek.

Included in the deal are 535 employees around the world and a production company in Switzerland.

Swatch makes and sells watches under 19 different brands including Omega, Longines and Tissot as well as has a retail chain under the Tourbillon Boutiques banner.

The mining company had been called Aber Diamond Corp. until it acquired the Harry Winston retail business in two stages in 2004 and 2006.

As Harry Winston Diamond, the company had adopted an integrated strategy that included mining, polishing and retailing of the precious stones.

However, the company has recently moved to increase the mining portion of its business by acquiring BHP Billiton's diamonds business, including its stake in the Ekati diamond mine in the Northwest Territories for $500 million US in cash.

Under the deal, BHP Billiton's employees working at Ekati, in Yellowknife and in diamonds marketing in Antwerp, Belgium, will join Harry Winston.