An online listing for the locket said it had been crafted from 18ct yellow gold and set with 60 white diamonds and 15 blue sapphires.
A golden octopus inside the locket was set with two black diamonds for eyes.
Officers from the Auckland City Beat team were on the scene minutes later, and arrested the man, police confirmed.
He had been charged with theft, and was remanded in custody when he appeared in Auckland District Court last week, he was expected to reappear next Monday.
Police told RNZ the pendant had not yet been recovered.
– RNZ