Gold nuggets are not like crystals, which form when molten minerals cool or when they precipitate from fluids moving through cracks and fissures in the Earth's crust. Instead, gold nuggets, whose impure composition typically contains 10 to 20 percent silver or copper, are shaped by what are known as hypogene processes, meaning they form deep beneath the Earth's surface at high pressure. Thus, what we see when we admire a gold nugget is a weathered shape, its fractured surface usually smooth and rounded, with pits and even holes showing where softer materials that were once nestled against the precious metal have eroded away.
While most gold nuggets in circulation today are no bigger than your thumb and no wider than a quarter, some notable gold nuggets are on the scale of fair-sized boulders, weighing as much as 150 pounds. Australia seems to be especially fertile ground for some of the world's largest gold nuggets, the biggest of which is known as The Welcome Stranger, which was discovered in 1869 in the southeastern state of Victoria. Measuring almost two feet across at its widest point and weighing more than 158 pounds, the prize was found only an inch or so below the surface, the roots of a tree holding it in place. A nugget named The Welcome, which weighed almost as much and tested out as 99 percent pure, had been found in the same state just 11 years earlier, only it was secreted 180 feet under ground.
Though most gold used in jewelry is melted and then formed into rings, bracelets, pendants, and earrings, sometimes small gold nuggets are left in their natural state, their irregular forms producing unique shapes that even an experienced jeweler would be hard-pressed to imitate. Often these pieces were made and marketed during some of the many gold rushes around the world. In the United States, strikes in California in 1849 and in Alaska in 1898 prompted jewelers to create souvenir pieces, often pairing a gold-miner's pick or shovel with a small nugget. Most expensive were gold nuggets encased in polished quartz, since hard-rock mining was the most expensive way of mining gold. By the time the Alaska gold rush had passed its peak, native Eskimos were routinely carving walrus ivory into good-luck figurines, which were often adorned with a small gold nugget.