Beachcombers are usually pretty content with a sea-sculpted piece of driftwood but Paul Mason struck lucky when he reached into a wave and plucked out a fine chunk of amethyst.

Mr Mason spotted something glistening in the water while he was walking along the seashore between Overstrand and Cromer about four years ago.

He has grown to love the precious stone and believes it has brought him good luck, But he has become increasingly intrigued about where it came from, how it ended up on a north Norfolk beach, and whether it is worth a small fortune - or a few pence.

The water-worn stone, in several shades of violet, is roughly lozenge shaped and about two inches long.

From his own researches, and a trip to UEA, Mr Mason, 47, from Cromer, believes his stone may have been in the sea for well over 1,000 years.

Possible origins include a Greek fishing boat - he has learned that fishermen carried an amethyst on their boats to guard against drunkeness; the word means 'not intoxicated' in Greek.

He also discovered that the Anglo-Saxons sometimes buried a piece with a body to help the dead person's passage to the afterlife.

And he understood that his stone may have been washed out of a mine in the Urals. Mr Mason is now considering having a laser test done on his amethyst to see what secrets it reveals.

Professor Julian Andrews, head of the School of Environmental Sciences at UEA, said amethyst was a variety of quartz and laser techniques could be used to determine the elemental content in the minerals but would not be able to identify its origins.

Colin Lansdell, secretary of the Norfolk Mineral and Lapidary Society, said the find was rare.

He thought the stone had probably arrived in Norfolk from Scotland by longshore drift rather than being carried by ice in an ice age.

'An ice transported stone would be smoother and rounder, as most quartz on our beaches, having been travelling longer,' said Mr Lansdell.

He was certain that the stone had not been washed from a Russian mine.

'The Greek ship idea is anyone's guess, and a bishop's ring is always an amethyst! Most gems recovered from Anglo-Saxon graves have been garnets but amethysts are not unknown,' he added.

It was very unlikely to be worth much. Being found in Norfolk added to its interest, but not value.

Mr Mason said that since finding the stone his life had changed. At the time his wife, aged 42, had been forced to give up her job because of ill health. Shortly afterwards she discovered she was pregnant and they now had a lively two-year-old son, Albert.

With Albert's arrival, the couple decided to sell their two-bedroom cottage in Roughton at the height of the rececession. They found a cash buyer who paid the asking price and bought a five-bedroomed house in Cromer without a mortgage.

Mr Mason, who used to work as a self-employed windscreen salesman, said he had been able to afford to stop work for a time and enjoy family life and that his own health had improved significantly.

Even if the amethyst did turn out to be valuable, Mr Mason said he would not want to part with it, adding: 'Some things you can't put a price on.'