Police have launched a public appeal to find the owner of $20,000 of gold bullion after a woman found it in her backyard on the state's south coast.

The woman discovered the gold in a package at her Kiama property last week and handed it in to police at Lake Illawarra police station last Thursday, July 14.

Lake Illawarra Sergeant Jason Harrison said he was appealing for the gold's owner to come forward, but he would be unable to describe its unique appearance.

"I'm not going to describe the gold any further other than it is described as gold bullion and someone that is missing gold would be able to give us more details about possibly what it was contained in and how it might be formed," Sergeant Harrison said.

"We're concerned that an item like this could be falsely claimed, with a gold bullion item it has limited marks and limited descriptions.

"It wasn't found loose, in her backyard, but I wouldn't go further to explain how it was located."

He said it was not buried and was in a part of her backyard where she had not previously seen any items.

Bullion may have been stolen, dropped in backyard

Sergeant Harrison said the bullion may not even come from the Kiama area and was possibly stolen and dumped or dropped in the backyard by the thief.

He said it "could be the case that they were stolen" and the "offenders have possibly dropped these items in a packaging in this woman's backyard".

The estimation of cost was based on the weight and the current value of gold, he said.

He said at the moment, the gold was locked at the police station.

"Perhaps an owner will be located and we'll be confident enough to hand it back, if that's not the case, we will explore what it means to remove these items to a more permanent location."

Owner may not know gold is missing: police

He said he hoped the media attention would alert the owner that the gold was missing.

"It's a very admirable thing that the woman has done, because someone's missing it ... through no fault of their own, perhaps they are now not even aware that it is missing.

"Perhaps they've stored it somewhere in a home or something and they are the victim of a crime that they are not yet aware of.

"This might reach out to some people ... who for whatever reason decided to store these valuable items somewhere and now they may determine after hearing a bit of talk about it that it's not there anymore."

He said the general position was that if you located an item and the genuine owner was not located after six weeks you could make a claim to have it returned to you.

The woman who found the gold had signalled she would like to keep it if no-one comes forward, so her identity would not be made public in case this does occur, he said.

Sergeant Harrison said there were markings on the gold that could identify it and he urged anyone that was storing gold in their home to check it and to get in touch with Lake Illawarra Police if it was not there.