SEATTLE — The fate of the mammoth tusk found at a construction site in downtown Seattle this week was entirely up to the landowner, a national expert said Thursday.

Washington state has no laws governing finds of this type. And Jack Horner of the Museum of the Rockies and Montana State University said that is true anywhere in the United States.

“Americans like their private land,” said Horner, one of the nation’s most famous paleontologists. Americans don’t like to pass laws putting restrictions on owners of private land, even to protect history, he said.

The landowner decided to donate the tusk to the Burke Museum of Natural History and Culture at the University of Washington, just as Horner hoped would happen.

It’s a relatively rare find and should be preserved for educational reasons, so children will know mammoth elephants once lived in Seattle, he said.

“A lot of times, people think these things are worth a lot of money,” Horner said. Their true value is educational, not what someone can sell a tusk for on eBay, he said.

Scott Koppelman, senior vice president of AMLI Residential, said after contractors found the fossil buried about 30 feet below street level, the company turned quickly to the Burke museum for assistance.

“The excavation will cause us some construction delay. But the scientific and educational benefits of this discovery clearly outweigh the costs and delay. This is an exciting discovery for our local Northwest history,” Koppelman said.

Mammoths lived all over the United States and Europe in ancient times, but finding a tusk or any part of those animals is rare, Horner said.

“We don’t find them every year or even every five years,” he said. In most cases, artifacts found at construction sites are destroyed before anyone notices them, Horner said.

Allyson Brooks, the Washington state preservation officer, said the situation would be different if workers had found human remains or other items or archaeological value because Washington state has laws for those situations.

With paleontological finds, the landowner can do whatever he or she wants, Brooks said.