Sterling Hill Mining Museum co-founder Richard Hauck told The Star-Ledger of Newark someone entered the museum between 12:30 p.m. and 1 p.m. Wednesday and smashed a plastic-glass cover.
Twenty gold pieces extracted from specific mines around the world were taken.
The nonprofit museum in Ogdensburg showcases the entire mining process through displays and tours of tunnels in an adjacent former zinc mine.
Hauck says the museum gets nearly 40,000 visitors a year.
Information from: The Star-Ledger, http://www.nj.com/starledger