Well that's exactly what's happened to a local man in the Gemfields, near Emerald in Queensland, 300 kilometres west of Rockhampton.

But the rock turned out to be a 753 carat sapphire.

The stone is larger than a golf ball and has been named the Sapphire Princess.

Pat Vine from Pat's Gems in the town of Sapphire was one of the first to see the precious stone.

She says in her 40 years in the area she's only spotted four or five that big.

"It looks a really nice stone," she says.

"You can see the blue through it, nice shape, it's like a big round sort of golf ball type shape and yeah, we were all pretty excited about it."

The stone was found by a local man who was 'specking' which is simply looking on the ground as you walk along.

"After rain the locals go out walking along and just look down where the water runs and on the mounds and the hills.

"You just casually walk along just trying to get something to catch your eye.

"The second lot of rain we had it was really big heavy showers and that's what you need for the run-off to wash the actual dirt off."

Jenny Elliot from Coolamon Mining at Sapphire is yet to see the Sapphire Princess.

But in her experience she says a large stone like that can be hard to deal with.

"Being 700 and whatever carats ... you wouldn't want to cut one stone out of it anyway, I think that would be crazy," she says.

"You'd have to ascertain first of all whether it has any defects in it and you would have to work around them when you were cutting it.

"In some cases a very big stone should be left as a piece of rough, as a specimen.

"People hang onto pieces of rough for a very long time, some sapphires are so beautiful in the rough that they lose their integrity, if you like, when you cut them.

"While they're not probably worth as much in the rough, they just have a certain beauty because nature made it and that's what's pretty clever about them."