The robbery occurred at about 11 a.m. at Joe Escobar Diamonds, located at 450 E. Hamilton Ave., according to police.
The incident began when three masked suspects walked into the store, displayed a handgun, and ordered all employees and patrons to the floor, police said.
The suspects then smashed a jewelry case and fled the scene in a silver Honda Accord or Toyota Camry with dark tinted windows, according to police.
Officers responding to the scene located the suspect vehicle and tried to stop it. A pursuit ensued through Campbell and onto southbound state Highway 17 at speeds exceeding 100 mph, police said.
During the pursuit, a Campbell police vehicle collided with an involved motorist, but no one was injured in the crash.
The suspect vehicle was last seen in the area of southbound state Highway 85 near Union Avenue, according to police. The suspects were all wearing dark clothing, masks and gloves.
The Campbell Police Department is asking that anyone who may have witnessed this robbery, or who has information about the suspects, contact Campbell police at (408) 866-2180.