A thief has struck Macalester College’s Science Building, where a display case of gold dust, small diamonds and precious stones was looted.

A lab supervisor reported the geological samples missing Tuesday night around 6 p.m., but authorities said the theft may have occurred sometime within the last week. Someone managed to break the lock and cut through plexiglass on the electronic revolving case in the building’s basement, said St. Paul police spokesman Steve Linders.

Among the items taken were silver, meteorite, platinum and other small minerals, including crystal quartz, ruby, opal and topaz — as well as their corresponding labels. The samples are believed to have “little or no value” if resold, Linders said.

Police said that the motive remains unclear and that the theft remains under investigation. No arrests have been made.

The Science Building and its basement exhibits are open to the public. Macalester’s fall classes began Aug. 31.