A pounamu carver told the Herald it would be difficult to gauge given there were various factors - including its grade and purity - that were taken into account and could not be entirely determined by looking at a couple of photos.
One thing that was certain, however, was that it had been in someone's possession at some point, he said.
"It certainly has had human hands on it. It's been cut down the middle - you can see it in the photo."
Several members of the public commenting on the Waikato Police Facebook page say it may have in fact been a memorial at the site and are calling on authorities to return it.
"Take it back to where it was found - sacred tapu," one woman writes.
Anyone with information about the greenstone is encouraged to call Police on 105
