Grinning with pride, a Chinese farmer held out two precious walnuts - globes so precisely symmetrical that consumers in search of hand massages value them more highly than gold.

"Prices have skyrocketed," said Li Zhanhua, standing in the shade of the leafy green walnut trees that have made him a small fortune. "Years ago, we could never have imagined this."

Rolling a pair of walnuts between palm and fingers has been a Chinese pastime for hundreds of years.

"Mainly the walnuts are good for the body, that's why people play with them," Li said.

Walnuts were used as toys in China's imperial courts as early as 220 AD, but were championed by officials during the Qing Dynasty (1644-1911) and have been a status symbol exchanged among the country's elite ever since.

Demand has grown alongside China's economic boom, and vendors say they are especially popular among the newly wealthy.

Years of rising prices have transformed the lives of farmers in Laishui county, a few hours from the capital.

Just a decade ago, Li and his neighbors plowed a hard-scrabble existence growing wheat and corn, but now take regular holidays from their mountainside village and own imported cars as well as apartments in a nearby city.

Li once sold a prized pair for 160,000 yuan ($27,000), but added: "Even a relatively ordinary pair of walnuts can be more expensive than gold, in terms of weight."

"We are all grateful for the huge changes the walnuts have brought us. All of our development depends on them," said Li, who says he harvests up to 2 million yuan a year from his nuts.

Collectors are not interested in the edible kernel, but instead value its ridged brown shell, which grows concealed beneath a green husk.

Farmers root through truckloads of walnuts to find pairs with the most symmetrical pits and ridges, which bring the highest prices.

Size - the bigger the better - and color also play a role, with deeper browns more valuable.

Different varieties' names are as colorful as the nuts themselves. There is the "government official's hat", whose pitted surface and form recall the tasseled headwear of Qing Dynasty courtiers, as well as the "chicken's heart" and "lantern", named for their shapes.