A gold nugget weighing almost half a pound was stolen Saturday from an exhibit at the University of Arizona.

The Flandrau Science Center and Planetarium, which houses the UA Mineral Museum, was open at the time the nugget was taken, but campus police have not released information about how the thief gained access to the nugget.

“We’re still investigating it and we’re trying to follow up with all the leads we have,” said Sgt. Filbert Barrera, spokesman for the UA Police Department. “We are looking to put the word out there because it’s a very unique and we need any type of information we can get.”

The nugget, part of the Hubert de Monmonier Collection, was stolen at about 2:30 p.m.

It measures 3.11-inches by 1.26-inches by .9-inch and weighs 7 ounces. The nugget is valued at $30,000 and “is well- known to the mineral community and museum enthusiasts,” Barrera said.

Anyone with information about the theft should call 911 or 88-CRIME.