"It's quite a loss," said Kay McClure, an employee of JFC Museum in Danville.
Employees of the museum say someone has stolen irreplaceable jewelry from their collection - worth around $15,000.
"It was nothing but diamonds - running anywhere from $1,000 to $5,000 a piece," said McClure.
Thursday morning a passerby noticed the door pushed in and a broken window.
Police say the burglary happened some time after 10 p.m. Wednesday.
Employees say the thief seemed to know his or her way around.
"They knew exactly where everything was at," said David Wilson, another employee, "it was planned."
The building is full of war and Indian artifacts, as well as antiques and old currency.
But the only thing that appeared to be touched was the jewelry case, which was filled with necklaces and rings. The burglar smashed the case to get to the jewelry.
The owner of the museum is out of town but has been notified.
The employees say the jewelry was not insured, and the theft is an insult to those who have put so much into the museum.
"(The owner) lets people come in at no charge, it's basically a community thing," said Wilson, "and then they come in and do him this way?"
They hope the jewelry is located, and that the person responsible is caught.
"Somebody needs to be an adult about it, take responsibility, or tell on who has done it," said Wilson.
Anyone with information is asked to contact the Danville Police Department