Hooded robbers made off with $2 million in gems and gold from the California Mining and Minerals Museum on Friday but failed to snatch the biggest prize - a 14-pound Gold Rush-era nugget.
The thieves entered the museum at 4 p.m. on Friday wearing face masks and night goggles and carrying pickaxes, reports the Los Angeles Times.
In broad daylight, they physically threatened a museum curator and a guide and herded employees into the far end of the building.
The employees were not injured during the heist but the California Department of Parks and Recreation, which operates the facility, said said they remained shaken by the experience.
According to AP, the thieves tried to snatch the museum's most valuable item - the 14 pound Fricot Nugget but triggered an alarm that alerted authorities.
The thieves managed to get away and so far there are no suspects.
Roy Stearns, the police department's deputy director of communications, told ABC news they stole an estimated $2 million worth of gems from the museum.
“We do not have a listing of items or the [value] of the amount stolen yet, as we are beginning a detailed inventory this week,” the department’s, Roy Stearns, told ABC News.
Police told AP that the unique pieces taken from the museum would be easily identified, which could make it difficult for the robbers to sell them.
“It is uncommon for most citizens to possess such minerals,” the CHP said in a statement.
It was the second time this year that rare, valuable metals were stolen in Northern California.
Historic gold nuggets mined by some of the first settlers in the remote California-Oregon border were stolen in February from the Siskiyou County Courthouse, reports the San Francisco Gate.
The gold stolen from the courthouse was valued at $3 million.
Authorities have not said if the two crimes are related.