A rugged wilderness tract in southern Mendocino County -- home to bald eagles, black bears and mountain lions -- has been donated to Sonoma State University by the family of a prominent San Francisco insurance executive.

Valued at $8 million, the 3,500-acre wildlands preserve off Highway 128 near Yorkville was a gift of the Fred B. Galbreath Trust, along with a $1 million endowment to pay for operations on the land.

At $9 million, it's the largest donation to SSU since 1997, when Telecom Valley entrepreneur Donald Green and his wife, Maureen, pledged $10 million for a concert hall to be named after them on the SSU campus. Construction of the Green Music Center is scheduled to start later this year.

"This is a piece of heaven," said Saeid Rahimi, dean of SSU's School of Science and Technology, which will operate the state park-sized preserve as a laboratory for biologists, geologists, geographers and even astronomers.

Rahimi, a techie who specializes in electronics and photonics, said the unexpected gift has kindled the nature lover in him.

"We fell in love with the pristine environment," Rahimi said, describing the ecological diversity of the preserve's forests, meadows, hills, streams and waterfall.

The university's first step will be a thorough survey and mapping of the property, a former sheep ranch that holds only some sheds and a network of no-longer-used logging roads.

Eventually, SSU hopes to establish a biological field station, a conference and retreat center and an observatory, the latter on one of the preserve's 2,000-foot peaks, far from intruding city lights.

"You can hardly find any darker skies," Rahimi said.

The university also hopes to open at least part of the property for public access, recognizing that much of it must remain undisturbed, he said.

Fred Galbreath's daughter, Nancy Johnson of San Rafael, said her father "would have loved the idea that it will be used by people who can study it the way he did."

Galbreath, who died in 2000 at age 98, was a marine insurance executive who once served as lead underwriter for construction of the Golden Gate Bridge, SSU officials said.

The connection between Galbreath's family and SSU was a successful alumnus, Long Beach stockbroker Tom Gillespie, a longtime financial adviser to Fred Galbreath.

An avid outdoorsman, Galbreath had often said the Mendocino County property should be donated to "higher education" but never specified a beneficiary, said Gillespie, a 1974 graduate who majored in economics and got a "great education" at Sonoma State.

He recommended SSU to Galbreath's family, got their consent and called the university to offer the $9 million gift "out of the blue," Gillespie said.

It took a year of quiet negotiations to work out the details, and two weeks ago the California State University Board of Trustees approved the bequest, Rahimi said.

More information about the preserve will be posted on a Web site at www.sonoma.edu/scitech and SSU plans to conduct a public contest to design a logo for the preserve.

SSU President Ruben Armiñana said the "spectacular preserve" will afford faculty and students "new opportunities for teaching and learning through environmental and interdisciplinary research projects."

While Galbreath's $1 million endowment covers operation of the preserve, Rahimi said SSU will raise money to develop the field station and other facilities.

The preserve, one of the largest in the California college and university system, will enable SSU to secure research grants, he said.