With the help of a neutron scanner, scientists at Los Alamos National Laboratory confirmed that a remarkable 217.78-gram specimen was, in fact, an enormous single crystal of gold— the largest ever discovered.
So rare is a single gold crystal of this size and weight that, although the precious metal is worth about $10,000, the specimen’s value is estimated to be $1.5 million.
The difference between a gold nugget and a gold crystal is that a nugget is formed from numerous crystals. The largest gold nugget ever found weighed 173 pounds.
A typical gold crystal is about 250 micrometers in size, or about 1/100th of an inch. The gold crystal specimen tested at Los Alamos National Laboratory was about the size of a golf ball, or 150 times the size of a normal crystal. It weighed slightly less than ½ pound.
The record-holding gold crystal, which looks like an origami flower, is owned by an individual from North Carolina, who collected this and other similar specimens over a 30-year period in the jungles of Venezuela. Seeking to verify whether four of his specimens originated from single crystals, he called in an expert in gold crystallography, geologist John Rakovan.
“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,” said Rakovan, a professor at the University of Miami.
Typically, X-ray analysis would be used to determine the crystal structure of an element, but gold is so dense that X-rays can’t penetrate deep enough. The geologist had to turn to neutron imaging technology instead.
The experts at the National Laboratory confirmed that three of the four specimens were single crystals. The trapezohedral specimen was determined to exhibit a more common multiple-crystal structure.
Photos courtesy of Los Alamos National Laboratory