OGDENSBURG, N.J. (CBSNewYork) — You could call it a gold rush in the Garden State – but for thieves.

Gold nuggets worth nearly $1 million were stolen from a mineral museum, CBS 2’s John Slattery reported.

On the site of a zinc mine dating back to the 1700s is the Sterling Hill Mining Museum, where crystallized gold and nuggets, 20 of them, were stolen while the museum was open. They were large specimens, from all over the world.

“The large nugget is from the Dominican Republic: a 16-ounce nugget,” said Richard Hauck, who assembled the collection.

Hauck said he put it all together 40 years ago at a cost of $400,000. He said today it would be valued at $750,000. The gold was displayed inside an antique safe behind sheets of heavy clear acrylic sheets.

“That someone would actually come here in the middle of the day when we are open and all those people here, and just do it,” Bob Hauck said.

Police said the daring heist happened between daytime tours, during a 20-minute window. Museum employees said the thief used an ax to smash the acrylic window, and then left the ax behind.

“He just grabbed it, threw in bag and over a fence he went,” Richard Hauck said, adding that there were no surveillance cameras operating at the time.

A $25,000 reward is being offered for the smash and grab that occurred in July of 2011. The directors of the non-profit museum decided to put the word out now because of four other museum burglaries around the country over the past two years.

But this gold is likely gone.

“Unless there’s some nutty collector who’s got it shoved under his bed someplace, but if anybody’s doing it for the money, they melted it,” Bob Hauck said.

The owners said they realize there is very little chance of getting the items back. They said it was a devastating loss since the gold was not insured.

The crystallized gold is worth more than gold nuggets. Both can be melted down, the Haucks said.

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