New Zealand's first $1 million diamond is unlikely to sit on a nearly-wed's finger or hang around the neck of a Parnell housewife, says Lior Sofer, of Beny Sofer Diamonds.

It is more likely to be a precious family heirloom "bought more for family purposes".

Win Charlebois, managing director of the Diamond Shop, where the Star of New Zealand was displayed for the first time yesterday, agreed.

But that didn't stop a huge amount of interest in the most expensive diamond ever to grace these shores.

I was asked to steal New Zealand's biggest and most expensive diamond even before I had seen it. "Can you put it in your pocket?" asked one reporter.

I was thinking the same, until I saw the security - a guard next to the case, and cameras trained directly at it. Smiling assistants surrounded the stone, in case I got any ideas.

A total of 19.5 carats seems excessive for a gemstone. But then you learn that it was cut down from a 52-carat raw diamond.

Wasn't that a bit wasteful?

"Every speck of the diamond is used," said Mr Sofer. "The diamond dust is used to cut other diamonds ... To cut a diamond, you need another diamond."

I asked Mr Charlebois the difference between a diamond and a crystal.

"A diamond is a crystal," he said.

"If you're buying a diamond for an engagement ring, you wouldn't want anything synthetic. Most women tend to desire something that's lasting, as it's a symbol of their relationship."

Said Mr Sofer: "The diamond is very rare. There's only a handful of diamonds in the world of this quality."

Mr Sofer would not tell me how he brought the diamond into the country, citing "insurance regulations".

The biggest diamond in the world is the 105-carat Koh-I-Noor (Mountain of Light), which was set into the tiara of the Queen Mother. The Star of New Zealand is less than a fifth of its weight.