Trustees of the cash-strapped Academy of Natural Sciences are selling more than 15,000 minerals and gems that haven’t been cleaned or displayed for decades in a deal estimated to be worth several million dollars.

Employees began boxing up specimens for an unnamed private dealer after trustees voted Tuesday for the sale, the acting academy president, Ian Davison, told the Philadelphia Inquirer for yesterday’s editions.

The city’s natural-history museum received permission for the sale from Orphans Court Judge Joseph O’Keefe. The academy must return to court for permission to sell its remaining 7,000-odd pieces — including silver, gold, diamonds, and everyday quartz — because William Vaux, who donated them 123 years ago, requested that they never be sold.

The academy, which has suffered staff cuts and a string of deficits, will use the proceeds to support its library.

Given that some of the minerals will end up with other museums, some say they are better off being sold and seen than locked behind closed doors. Yet the move has led to criticism of the world-renowned, 194-year-old institution, which is home to 17 million fossil, plant, and animal specimens.

Opponents include the great-greatniece of William Vaux, Trina Vaux.

“I think the entire collection represents a really important part of Philadelphia’s heritage,” Ms. Vaux, who lives in Bryn Mawr, said. “This is really the cradle of American mineralogy.”

But Mr. Davison said the items have been shut in a vault for most of the last half-century. Some specimens are crumbling and will have to be thrown out, he said.

And according to a court petition filed by academy attorneys, the museum has had no mineral lab or curator since the 1950s, except when a grant was used to hire one between 1976 and 1981.