Valuable Gold Rush artifacts were stolen from the Oakland Museum of California in separate burglaries over the course of two months, according to police.

A quartz and gold box dating to the Gold Rush was taken in the early morning hours on Monday, say reports. The object depicts scenes of early California and could be worth $800,000 although museum officials have called it an invaluable piece of history.

A reward may be announced for "the safe return of the object."

A break-in in November took place in a gallery housing American Indian artifacts, historical photos, and tools and mining equipment from the Gold Rush.

Surveillance video captured that burglary.

The museum is next to an Alameda County courthouse.