The discovery was made in the town of Ballarat in the Australian state of Victoria.
According to the BBC, this is the biggest gold nugget local experts have ever seen:
"I have been a prospector and dealer for two decades, and cannot remember the last time a nugget over 100 ounces (2.8kg) has been found locally," said Cordell Kent, owner of the Ballarat Mining Exchange Gold Shop.
"It's extremely significant as a mineral specimen. We are 162 years into a gold rush and Ballarat is still producing nuggets - it's unheard of."
The caption of a video posted on YouTube showing off the nugget told more of the story:
This 177 troy ounce gold nugget (5,505 grams - 5.5kgs) was found by a prospector with a hand held metal detector near Ballarat, Victoria, Australia on January 16, 2013.
What a find!!! No it wasn't me.... It was found at a depth of a little over 60 cm (2 ft) with a modern detector with a small coil. The prospector said it sounded like the bonnet of a car through the head phones. It was lying flat (broad side up) and he carefully dug it up. In this video it hasn't been cleaned. It is approximately 220mm long, 140mm wide and has a maximum depth of 45mm.
Ok, this nugget was found with a Minelab GPX5000 super metal detector, with an Advantage Plus 'Sadie' mono elliptical coil, and a Rooster Booster audio enhancer (used with an external speaker).
The prospector said he heard the signal, kicked off about 100mm (4 inches) of leaf mulch from the surface, and thought the ground looked in original condition ie it hadn't been dug previously.
It was lying flat in the ground, and was over 60cm (2 feet) deep in the earth/clay/gravels. So this means he and his detector heard it at an incredible depth from the search coil (the disc that is at the end of the hand held detector).
Kent told the Courier Journal that despite market prices, the nugget is actually worth more than $300,000 due to its novelty. "There's nothing like digging up money," he said. "It's good fun."