Minds are ticking after a strange metal ball was unearthed from the Grey River shingle pit, at Kaiata.
Westroads worker Chris Chamberlain was screening gravel when he noticed a rusted ball among the gravel.
"It looks like a miniature mine but I think it is far too small for a mine," Mr Chamberlain said.
"At first I thought it was an odd looking rock. I'm quite fascinated with odd bits of metal which come across the screen and when I had a closer look I saw it was rusted. It's not big and definitely not a mine, but I hope History House can work out what it actually is and what it was used for."