The "King Henry" gold rock specimen was discovered half a kilometre underground at Beta Hunt in WA's Goldfields region in 2018 by airleg miner Henry Dole.

It contains an estimated 45kg or 1400 ounces of gold worth more than $3 million.

Industry experts estimate it is likely in the top five largest of its type to ever unearthed.

Sitting next to "King Henry" is "The Karratha Queen", a silver nugget found in 2000 at the Elizabeth Hill mine, 45km south of Karratha in WA's Pilbara region.

It contains about 99.79kg or 3520 ounces of silver, worth $136,000 in metal alone.

The Perth Mint acquired "King Henry" in 2019, while "The Karratha Queen" is on a long-term loan from the Shemesian family.

Together, they form a new display opened to coincide with a major refurbishment of the mint's foyer and retail showrooms.

"The two precious displays epitomise so much of what The Perth Mint has experienced since its foundation 122 years ago," said chief executive officer Richard Hayes.

"Mining, gold refining and fabricating techniques may have changed but our pursuit of the highest-quality gold and silver has withstood the test of time."

Unlike a nugget, which is traditionally found at or near surface and mostly contains pure metal, "King Henry" is classified as a gold specimen, which is a gold-encrusted rock recovered from an underground lode, or gold-bearing quartz vein.

The second-largest Australian gold nugget, "The Normandy" is already on display at The Perth Mint.

It weighs in at 819 ounces or 25.5kg.

The largest existing Australian nugget is "The Hand of Faith", which weighs 875 ounces or 27.2kg and can be viewed by the public in the Golden Nugget Casino Hotel in Las vegas.

Australian Associated Press