Thieves smashed the front window of a downtown Vancouver store and made off with a rare Canadian gemstone worth half a million dollars, police said.

The 11-inch (279-millimetre) ammolite gemstone, which is made of the fossilized shells of ammonites and is found primarily along the eastern slopes of the Rocky Mountains, was stolen from Gastown's Gems and Rocks at 313 Water St. around 4 a.m. PT Friday.

Ammolite is the official gemstone of Alberta and is considered a Canadian national treasure. Police said an application to the Canadian government must therefore be made for it to be removed from the country.

While police wouldn't say the incident was a planned burglary, store employee Zee He told CBC News the gemstone was the only item taken during the break-in.

"Video camera inside has recorded the whole process. Took them about three minutes for the whole crime to happen," He said. "It's definitely been targeted."

He added that the surveillance video shows one suspect keeping watch while another smashes the window and makes off with the stone.

Anyone with information is asked to call Vancouver police or CrimeStoppers at 1-800-222-TIPS.