Greenstone (pounamu) is much more than a commodity to Mark Solomon.

"It's a special stone - it's hard to put into words. I always wear pounamu against my skin. It becomes part of you," says the kaiwhakahaere (chairman) of South Island tribe Ngai Tahu.

"There's a whole history within the Ngai Tahu family of connections with pounamu. It has huge significance."

It is why Mr Solomon and others in the tribe take it personally when the prized South Island greenstone reserves they have legal ownership of are targeted by thieves.

After private investigations by Ngai Tahu, police are prosecuting people for thefts from the remote South Westland region.

Yet some in the greenstone industry deny the thefts are taking place, because they dispute Ngai Tahu's right of ownership vested in the tribe by the Government in 1997.

"In the first instance ... Ngai Tahu are the thieves. (Pounamu) was never the Government's to give to them," says greenstone carver Bevan Climo, a former member of the Ngai Tahu Pounamu Management Group.

"They are holding on to it for grim death because they think it is worth billions and billions of dollars."

This week renowned search and rescue helicopter pilot Harvey Hutton was sentenced to 18 months' jail and ordered to pay $300,000 for stealing up to 40 tonnes of the stone from South Westland between 1997 and 2004.

Hutton claimed he had a right to the stone and is appealing against his conviction and sentence.

Father and son pilots David Anthony Saxton, 60, and Morgan David Saxton, await trial for theft of greenstone belonging to Ngai Tahu over a period of nine years.

Ngai Tahu believe these cases may be just the tip of the iceberg. Solomon says millions of dollars may have been lost to greenstone theft in recent years.

"For a long time now we have known that [black market greenstone] is quite a big industry. We all know it is happening, but it is getting the evidence," Mr Solomon says.

Mr Climo, who is part of the kaitiaki (guardians) of greenstone in South Westland, says suggestions of a thriving black market are nonsense.

"The only black market is my cousins out there running around the creeks looking for it and selling it. This is just the media hype and bull**** they put up to cover their arses."

In reality, Ngai Tahu, with its headquarters in central Christchurch, can do little to stop theft of greenstone from the remote parts of the South Island.

"To be honest, I suppose the best security is the eyes of the community. When you live in communities like the West Coast, which are pretty isolated as far as numbers go, the locals they see things, they know what's happening."

Mr Solomon says the jail sentence given to Hutton this week is important.

"It sends a clear signal that the court will support us in cases of theft. You do the crime, you pay for the crime. Just helping yourself willy-nilly to anyone else's property is just not part of our society. It's not acceptable."

But Maika Mason, chairman of West Coast Maori land authority, the Mawhera Incorporation, says the sentence given to Hutton is inadequate and the justice system is "weak-kneed" when it comes to greenstone theft.

"We are looking at the future relations in this country with Maori. The courts needs to look at those sort of things and see who is making the money out of this."

Hutton was a man with money and technology "and he's stealing from the little people in this country" who could not access the greenstone that he could.

Mr Solomon and Mr Climo agree there is a problem with imported greenstone, or jade, being sold as New Zealand pounamu.

"When it is sold as pounamu, we want to ensure it is genuine. That is important to us," Mr Solomon says.

Mr Climo says the whole greenstone industry is in a "big kerfuffle" at present because of the lack of stone being obtained.

The allure of pounamu

* Greenstone is the name European settlers in New Zealand gave to nephrite or jade. The Maori named it pounamu.

* Pounamu is found on the South Island's West Coast in Greymouth and Hokitika and in the Dart Valley River near Queenstown.

* The Government vested ownership of the South Island's greenstone stocks to Ngai Tahu in 1997. Kaitiaki (guardians) around the South Island are entrusted with the responsibility for it.

* After disputes over existing greenstone mining licences, including one case that went to the Privy Council, all private mining rights are now ended. The exception is the Mawhera Incorporation, which has rights to greenstone in the West Coast's Arahura River catchment.

* Anyone may collect a piece found on the West Coast if it can be personally carried.

* The value of pounamu lies predominantly in the labour and skill used when working with it. The more intricate the work, the more expensive the pounamu. A basic pendant (1.5cm x 3cm) may retail for $30 and an intricate one of the same size may sell for $150.

* Pounamu wholesale trade rate: Sold by the pound, $20 to $40 a pound (0.4536kg). Good pieces may sell for up to $1000 a pound.