"I ordered a seafood dish that was clams and mussels with linguine in a white-wine and lemon sauce," Hasz told the Seattle Times. "About midway eating through my meal, I bit down on something hard. I almost broke my tooth, it was so hard."
Hasz said she spit out the object and found it appeared to be a pearl.
"I thought maybe it was an earring from an employee in the kitchen and it fell into my dish," Hasz told KOMO-TV.
The diner said she took the object home and her curiosity was piqued when she noticed a purple tint to the sphere.
"When I Googled this pearl, I found a very specific kind of pearl called a Quahog pearl. They're very rare. I saw some on sale online for thousands of dollars," Hasz said.
Hasz took the pearl to Ted Irwin of Northwest Geological Laboratory in Bellevue.
"He thought it looked so round and perfect that someone was playing a joke on me," Hasz said.
Irwin confirmed he was initially skeptical.
"I have heard that scenario in my 35 year career and it has turned out to be nothing much," Irwin said.
However, Irwin was able to confirm the object was a Quahog pearl of gem quality.
"One in a couple million is of gem quality, so it is a very rare occurrence," Irwin said.
Irwin estimated the 1-carat pearl's value at about $600.
Montalcino owners Fernando and Cindy Nardone joked their workers are keeping a closer eye out for pearls in the clams that pass through the kitchen.
"It shows we serve nothing but the best," Cindy Nardone told The Issaquah Press.
