Gold nuggets are naturally occurring large masses of native gold found in alluvial deposits. Often they are concentrated by watercourses and recovered by placer mining. In other instances, gold nuggets are found in piles of residue in sites where mining operations once took place.

Two gold nuggets are noted for being the largest masses of gold ever discovered. These are the "Welcome Stranger" and the "Hand of Faith". Their respective "largest" titles, however, carry further qualifications.

The Welcome Stranger Gold Nugget:

The exact distinction given of this gold nugget is: "the largest alluvial gold nugget ever found". It was discovered on February 5, 1869 at Moliagul, a small township in Victoria, Australia about 37 miles west of the city of Bendigo. The discoverers, John Deason and Richard Oates, found the nugget just a couple inches below the surface on a slope in a place that's sometimes called Black Reef.

Records have the following details about the Welcome Stranger:

• Gross weight: 3,523.5 troy ounces (241.61 pounds)

• Trimmed weight: 2,520 troy ounces (172.8 pounds)

• Net weight: 2,315.5 troy ounces (158.78 pounds)

• Measurement: 2 feet (0.61 meter) x 1.02 feet (0.31 meter)

For their find, Deason and Oates were paid about £19,068 by the London Chartered Bank (located in the town of Dunolly in Victoria), where they took the nugget.

The Welcome Stranger no longer exists today, although the gold from it understandably still does. Also, there exist two replicas of the nugget. One is in possession of the descendants of John Deason, while the other is in the City Museum in Treasury Place, in Melbourne.

The Hand of Faith Gold Nugget:

This gold nugget actually carries two distinctions: "the largest gold nugget found by a metal detector" and "the largest gold nugget currently in existence". It was discovered on September 26, 1980 somewhere near the small town of Kingower in Victoria, Australia.

The nugget's discoverer, Kevin Hillier, was aided by a metal detector in this precious find. Hillier found the nugget in a vertical position just a foot below the surface.

The Hand of Faith weighs 874.82 troy ounces (60 pounds) and measures 1.54 feet (0.47 meter) x 0.66 feet (0.20 meter) x 0.30 feet (0.09 meter). The Golden Nugget Casino in Las Vegas, Nevada currently houses the nugget. Its sale price was reportedly around 1 million U.S. dollars.

Gold nuggets actually are not composed of pure 24K gold. A safer estimate would be that they're somewhere between 20K and 23K. Those found in Australia often have higher purity than the ones found in Alaska. The color of a nugget often provides a clue as to the purity of its gold content. Nuggets that have very rich deep orange/yellow color are sure to have higher gold content than pale ones.

Also, there is a system called "millesimal fineness" which is used to denote the purity of gold alloy (also of silver and platinum alloys) by parts per thousand of pure metal by mass in the alloy. A nugget containing 91.6% gold, for example, is denoted as "916 fine". This fineness is equivalent to 22K.