BEIJING (NYTIMES) - One summer day, a Kazakh herder in northwest China noticed that a giant black boulder had appeared overnight in the grasslands where he raises sheep and cattle. He left it there, and it sat undisturbed for more than two decades.

But in 2011, local officials declared the rock a meteorite and hauled it away, arguing that natural resources were state property. So the herder and his sons decided to sue.

"The meteorite wasn't made on land, or even on the earth," the family's lawyer, Sun Yi, said in a telephone interview from Shanghai.

"It's from outer space, so it should belong to the person who first discovered it."

The case opened in the Xinjiang autonomous region last month after years of legal wrangling, and a verdict is expected within six months. Legal experts say it highlights how the private land-use rights that China's governing Communist Party introduced in the 1980s - in a country where all land is owned by the state - are so broadly defined that they often sow confusion.

But the case is also unique, experts say, because it exposes what is essentially a legal black hole: Chinese statutes do not clearly indicate who owns property with intergalactic characteristics.

"We're left with a blank, a vacuum, in Chinese law, with no definition of natural resources and no clear saying as to whether meteorite rights belong to the state," said Zhang Libin, a lawyer in Beijing who advises the government on legal reform in the energy and minerals sectors.

The Xinjiang meteorite weighs 17.8 tonnes and is made of siderite, or iron carbonate, according to a report in the Chinese news media that cited an official research center.

Sun said he thought it was worth nearly US$320 million based on his understanding of the commercial meteorite market. But Tong Xianping, a meteorite collector in Urumqi, the Xinjiang capital, said by telephone that US$24 million was a more realistic value based on what he estimated was the rock's per-gram value of about US$1.45.

Eric Twelker, founder of the Meteorite Market, an online emporium based in the United States, said he doubted that the Xinjiang meteorite was worth millions of dollars because he rarely saw specimens of any size selling for much more than about US$30,000.

"Once you get into something like 17.8 tonnes, your market is infinitesimally small," Twelker said in a telephone interview from his home in Port Townsend, Washington.

China is not the only country where meteorite claims have led to court battles.

In the United States, an 1892 decision by the Iowa Supreme Court established that a meteorite belonged not to the prospector but to the landowner, according to the 2006 book "The History of Meteoritics and Key Meteorite Collections: Fireballs, Falls and Finds."

Anotherlandmark court decision awarded a meteorite that was discovered by prospectors in 1976, on federal land in California's Old Woman Mountains, to the government.

The "Old Woman Meteorite" was later sent to the Smithsonian Institution in Washington, and Twelker said the case had established a legal framework of sorts for contemporary prospectors.

"It's the story of treasure hunters and the government everywhere," he said. "If the government can get your treasure, they will."

In 1986, the herder in the Xinjiang case, Juman Reamazhaen, was told by local officials that he could keep the meteorite, according to his son, Teliewubieke Juman. But in 2011, a team of government workers went to the family's property in Kuoleteke village to seize it.

Reamazhaen and his two sons insisted that the meteorite was theirs, and they took turns protecting it in round-the-clock shifts through the summer and early autumn, Juman said. But a few months later, when they ended their vigil because of cold weather, the workers swooped in.

The meteorite now sits in a wooden crate outside a government office in the nearby city of Altay. Sun, the lawyer, said that to his knowledge, the government had not conducted any scientific tests on it. Local officials did not respond to a faxed request for comment.

Legal experts say the herders' case boils down to whether a clause in Chinese law that defines natural resources as state property - in which the word "et cetera" appears at the end of a list of natural resources that includes mountains, grasslands and wetlands - should apply to things from outer space.

"Both sides seem to have an argument which is seemingly right, but there is no clear answer," said Zhang, the legal adviser in Beijing.

"The state says if the law says 'et cetera,' then you can certainly include meteorites. But then it goes to the question of how to define natural resources."

Zhang said similar, although not identical, questions were bound to surface as the Chinese government granted concessions on state land to more coal, geothermal, and oil and gas companies.

He said the government could avoid future property disputes by sharpening its minerals and natural-resource statutes.

For the moment, though, property disputes between stubborn farmers and powerful officials are common, and they seem likely to continue as China urbanises at a breathtaking pace.

Susan Finder, a scholar in residence at the Peking University School of Transnational Law in the southern city of Shenzhen, said the overwhelming trend in Chinese property disputes was that courts favoured officials over ordinary people.

"It's all related to this tension between the huge power of the state and the limited scope for an individual to protect his or her property rights," she said.

In the Xinjiang case, Reamazhaen would consider negotiating for a compensation fee if Chinese authorities determined that the 17.8-tonne meteorite could be useful for scientific research, his lawyer said.

His son, however, appeared less willing to compromise.

"I have visited our local government bureau several times and saw some guards standing around the meteorite," he said by telephone. "Were they protecting it? Hard to say. In any case, we are not happy with the way they've handled this situation, and we will keep suing the government until we get a satisfactory result."