Chinese buyers have descended on the world's largest amber fair this week in the Polish Baltic port city of Gdansk, amid a boom that has seen the price of the fossilised tree resin spike tenfold in eight years.

Despite an economic slump in China, merchants say amber sales there are still booming due to its popularity as a good luck charm and health tonic.

"Chinese people think amber is good for their health. Many, many Chinese medicines have amber," Zhang Zhiping Zhang, a 30-year-old Chinese merchant, told AFP as he looked for new merchandise at the fair.

According to fellow Chinese amber merchant Wang Hao, "amber is very much part of our culture and it is believed to bring good luck."

China recently surpassed the United States as the world's largest consumer of amber, of which there are more than 300 varieties.

"There's an amber craze in China, due to its great cultural, religious and medical significance," Ewa Rachon, head of Gdansk's Amberif fair, told AFP.

This year the annual amber extravaganza attracted nearly 500 sellers and over 6,000 visitors.

"Since 2008, prices have spiked tenfold," Rachon said.

According to Michal Kosior, deputy president of the Gdansk-based International Amber Association, one kilogram (2.2 pounds) of raw amber now sells for several thousand euros, depending on its colour and whether it contains inclusions like prehistoric insects or vegetation.

With a steady client base of around 1,000, Zhang says that while five years ago sunny yellow amber was all the rage, now tastes have changed and creamy white amber is more popular.

Some specimens sparkle like champagne with tiny prehistoric air bubbles, others look like swirls of honey and butter.

Pieces with a blue-green tinge are the rarest and most valuable.

Rich veins of this 40-million-year-old fossilised tree resin running along Poland's Baltic coast have fuelled a centuries-old trade in Gdansk, positioning it as the world's amber capital.

Deftly crafted beads, bracelets and amulets dating back 5,000 years to the Neolithic Age attest to the timeless appeal of the organic treasure.

Amber deposits in Poland and nearby Kaliningrad and Lithuania are estimated at 650,000 tonnes, easily the world's largest concentration.

Smaller amber deposits are spread across the globe from Canada to South America and Australia, through to Africa and Asia as well as the Middle East.

Polish customs said Wednesday they had seized a record 1.5 tonnes of amber worth an estimated six million euros ($6.6 million) on the border with Ukraine, with some stones "the size of an ostrich egg".