So when a man on Thursday afternoon asked if he could touch the $139,000, one-of-a-kind, half a kilogram solid gold chain with diamonds, acting store manager Hannah Johnson didn't think much of it.

But as soon as the chain came out of the drawer the man, who had been chatting casually, "switched" and became "aggressive", Ms Johnson said.

He snatched the chain and took off running through the shopping centre.

"It just happened really quickly," Ms Johnson said. "I didn't even really have a chance to say anything. I got it out and I was leaning over to show him and before I knew it he just grabbed it and legged it."

Ms Johnson was shaken but not injured and called police and security immediately.

Fortunately, police officers were only a few stores away and gave chase, arresting the man and recovering the chain.

Simon Curwood said Ms Johnson "remained calm and alerted authorities", praising her for her quick thinking and labelling her a "hero".

Ms Johnson had been working the floor alone when the man approached and began asking about the chain, saying he was expecting a large payout and had owned a similar chain in the past.

She said the chain was a "talking point" in the store and people were often asking about it.

"Everyone who walks passed knows it," she said. "We're used to people chatting about it and wanting to see it or touch it."

Jewellery store snatch and grabs like the one on Thursday are relatively uncommon in the Hunter and Ms Johnson said it was the first time it had happened at Greenhills.

The Newcastle Herald reported in 2017 about a thief who stole more than $65,000 worth of diamond rings from Michael Hill at Charlestown.

Police said that while the three sales staff members were busy, Joshua Johnson reached over the display counter into the cabinet and removed two trays containing 32 diamond rings.

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