World's Largest Gold Crystal Found

World's Largest Gold Crystal Found

The world's largest gold crystal was found in Venezuela in the 1930s, but it wasn't until 2015 that scientists at Los Alamos National Laboratory were able to confirm its authenticity and size.

The crystal, which is about the size of a golf ball, weighs 217.78 grams (about 7.7 ounces) and is estimated to be worth over $1.5 million. The crystal is about the size of a golf ball and has a rough, irregular surface. It is currently on display at the Los Alamos National Laboratory in New Mexico, USA.

The crystal was discovered by a gold miner in the El Callao gold district in Venezuela. The miner was working in a placer mine, which is a type of mine that extracts gold from loose sediments. The miner found the crystal in a pan of sediment that he had collected from the streambed.

The crystal is made up of a single crystal of gold, which is very rare. Most gold found in the Earth's crust is made up of many small crystals. The crystal is also very pure, with a gold content of over 99%.

 
World's Largest Gold Crystal Found
Researchers at Los Alamos National Laboratory have determined that this is the world's largest single crystal of gold.
Photo: John Rakovan

The lump of gold was brought to Los Alamos to confirm whether it was a single crystal of gold, or a more common multiple-crystal structure. "The structure or atomic arrangement of gold crystals of this size has never been studied before, and we have a unique opportunity to do so," Miami University geologist John Rakovan said in a statement.

"The structure or atomic arrangement of gold crystals of this size has never been studied before, and we have a unique opportunity to do so," the Miami University professor said.

Revealing the inner structure of a crystal without destroying the sample—imperative, as this one is worth an estimated $1.5 million—would allow Rakovan and Lujan Center collaborators to prove that this exquisite nugget, which seemed almost too perfect and too big to be real, was a single crystal and hence a creation of nature. Its owner, who lives in the United States, provided the samples to Rakovan to assess the crystallinity of four specimens, all of which had been found decades ago in Venezuela.

During the past Lujan Center user run cycle, Heinz Nakotte, New Mexico State University professor and lead scientist for the single-crystal diffraction (SCD) instrument, and Sven Vogel, instrument scientist for the high-pressure/preferred orientation (HIPPO) instrument, helped Rakovan probe the stunning pieces at Los Alamos. The authors are preparing a scientific report.

Three of the four samples turned out to be single-crystal pieces of gold, rather than the commonplace multiple-crystal type. Of particular interest was a golf-ball-shaped nugget that at one time was believed to be the world's largest trapezohedral gold crystal. In 2006 the crystal had been rejected at auction over questions of authenticity, and indeed, the Los Alamos instruments confirmed that it was not a world-record trapezohedral crystal.

Further interpretation of the results will also provide an understanding of how the rare pieces may have formed before they were slightly deformed while being washed down in ancient stream sediments. The ability of the HIPPO instrument to also show how far away a specimen is from being a single crystal helps with these interpretations.

The SCD instrument is a neutron single crystal diffractometer used to determine the periodic atomic arrangement or crystal structure of single crystals, both natural and synthetic. While one of the workhorse-instruments at the Lujan Center, HIPPO is a general-purpose powder diffractometer that measures both the crystal structure and orientation distribution of crystals (or texture) making up a poly-crystalline material from the powder pattern of the crystals. It is the only time-of-flight neutron instrument in the world that routinely measures texture, with single crystals being the ultimate textured samples.

"The gold single crystals are so far the largest single crystals characterized on HIPPO," Vogel said. HIPPO handles a wide range of materials including rocks, battery materials, alloys, and nuclear fuel mock-ups.

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The above story is based on Materials provided by Los Alamos National Laboratory.
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