10 Lustrous Facts About Gold

This 6.5-pound gold nugget was sold at auction in 2010.
This 6.5-pound gold nugget was sold at auction in 2010.
Robyn Beck/Getty Images

Gold’s symbol on the periodic table, Au, comes from its Latin name aurum, which means “glowing dawn.” This metal’s tantalizing yellow color and shining exterior has made gold a prized element in jewelry and treasured objects for thousands of years—but, amazingly, all of the gold that has ever been refined could melt down into a single cube measuring 70 feet per side. Read on for more opulent facts.

1. GOLD WAS PROBABLY THE FIRST METAL USED BY HUMANS.

Gold, number 79 on the periodic table, is almost twice as heavy as iron, but it’s incredibly malleable—and for that reason, it was probably the first metal humans ever wrought. The oldest known worked-gold artifacts, from the Thracian civilization in present-day Bulgaria, date back 4000 years; the death mask of the ancient Egyptian pharaoh Tutankhamun contains about 220 pounds of gold. Despite its presence in world cultures for millennia, “more than 90 percent of all of the gold ever used has been mined since 1848,” according to the American Museum of Natural History. That year marked the discovery of gold at Sutter’s Mill, California, launching the California Gold Rush.

2. ALL OF THE GOLD IN THE UNIVERSE MAY HAVE COME FROM COLLIDING NEUTRON STARS.

In 2017, astronomers from the University of California, Berkeley and other institutions observed two massive neutron stars spinning around one another at an accelerating rate. When the two stars—each with a mass up to twice that of our Sun—finally collided, gravitational waves rippled through the universe and clouds of neutron-rich material shot out. For the first time, researchers observed red light emanating from the collision, indicating the production of heavy metals like uranium, gold, and platinum. The finding supports the theory that all of the gold in the universe was formed this way—and that particles of that gold arrived on Earth in meteorites billions of years ago.

3. IT’S AN EXCELLENT CONDUCTOR OF ELECTRICITY.

Gold efficiently transfers heat and electricity—though not as well as copper and silver. In general, some metals conduct electricity well because their atoms share electrons easily: As electrical current flows, electrons move along in the same direction with just a little voltage. (The opposite would be true of insulators like glass, in which electrons move only when compelled to do so by thousands of volts of electricity.) Because gold resists oxidation and corrosion, it continues to move electrons even if occasionally exposed to the atmosphere. That’s why electrical contact surfaces are plated with a microscopic gold coating in smart phones, airbag sensor modules, and other devices.

4. YOU CAN FIND SUNKEN TREASURE, BUT YOU MIGHT NOT GET TO KEEP IT.

In 1985, Florida diver Mel Fisher located the Nuestra Señora de Atocha, a famed Spanish naval ship loaded with valuables that had sunk in a hurricane in 1622. Fisher’s motto was “finders, keepers”—and in the following decades, he retrieved gold, silver, emeralds, and pearls worth millions of dollars. Under admiralty law, Fisher was entitled to keep what he found, but archaeologists, historians, and conservationists protested. Two years after the discovery, Congress passed a law stating that riches found in wrecks within three miles of a U.S. coastline belong to the adjacent states.

5. GOLD CAN BE MEASURED WITH A UNIT FROM THE MIDDLE AGES …

The gold standard is a monetary system that ties a currency’s value to gold itself, which theoretically keeps inflation in check. The United States adopted this standard in 1879, but began to abandon the system in 1933 to stimulate the economy at the height of the Great Depression. The U.S. got rid of the gold standard entirely in 1971.

However, the U.S. Treasury still holds on to 261.5 million fine troy ounces of gold, using a unit of measurement that dates to the Middle Ages and is named after the city of Troyes, France. (A troy ounce is a few grams heavier than a regular ounce.) The goods are in the form of gold bullion (bulk gold shaped into bars), as well as coins and miscellaneous units, and stored in vaults at federal mints and reserve banks. As of September 2017, the government’s gold reserves total $335.5 billion in market value.

6. … OR IN BREAD.

Gold’s value has remained surprisingly steady over time. “King Nebuchadnezzar of Babylon, reigning in the 6th century BCE, bought 350 loaves of bread for an ounce of gold,” John Mulligan, head of member and market relations at the World Gold Council, tells Mental Floss. Roughly 2500 years later, with the current price of gold at about $1200 per ounce and a loaf of bread at $2.50, an ounce of gold would buy 480 loaves. “If we also then look at how gold compares with the historic purchasing power of the world’s major currencies over the last century or more,” Mulligan adds, “we see none of them has endured like gold.”

7. GOLD MIGHT HELP DESTROY CANCER.

“Gold just sits there and shines when it’s [in a] large [mass]—it doesn’t do much,” Mostafa A. El-Sayed, a leading chemist at the Georgia Institute of Technology, tells Mental Floss. “But when you cut it smaller and smaller, all of the sudden, it has different properties.” In a 2017 paper in Proceedings of the National Academy of Sciences, El-Sayed placed gold nanorods in mice with tumors and zapped the nanorods with a laser. The rods became hot enough to kill the adjacent cancer cells. Fifteen months later, the mice showed no long-term toxicity. In the paper on these findings, El-Sayed and his co-authors called this “a strong framework” for trying the technique in humans.

8. GOLD HAS BEEN USED IN DENTISTRY FOR AT LEAST 4000 YEARS.

Gold’s combined properties of malleability and biocompatibility (i.e., it can be tolerated inside the body) have made it useful in dentistry. Archaeologists have found gold dental modifications in skulls from Southeast Asia dating back 4000 years. The Bolinao skull, an artifact from the 14th or 15th century, is one of 67 skulls featuring decorated teeth that have been excavated in the Philippines. Ten-millimeter-wide gold plates are fixed in place on the incisors and canines in an overlapping fish-scale pattern. Today, gold-alloy crowns are still used to cap worn-down teeth or to strengthen weakened teeth.

9. NASA USES GOLD IN SPACE TECHNOLOGY.

The visors of astronauts’ space suits are coated with a layer of gold that’s just 0.000002 inches thick. The coating shields their eyes from the Sun’s harmful infrared light while allowing visible light in. That same ability to reflect infrared light will be put to work in the James Webb Space Telescope as it searches for light from the first stars and for potentially habitable exoplanets. The telescope will be equipped with 18 hexagonal mirrors in a honeycomb-like structure. Three grams of gold were vaporized in a vacuum chamber and then adhered to the telescope’s mirrors, which are made of beryllium. The layer of gold is just 100 nanometers thick—a tiny fraction of the thickness of a sheet of paper.

10. COLORADO’S CAPITOL BUILDING IS GILDED WITH PURE GOLD LEAF.

At least 10 state capitol buildings have gold-topped domes: Colorado, Connecticut, Georgia, Iowa, Massachusetts, New Hampshire, New Jersey, Vermont, West Virginia, and Wyoming. Colorado’s dome was restored in 2013 using about 65 ounces of pure gold that was mined in the state and hammered into leaves between one-8000th and one-10,000th of an inch thick. Gilders applied 140,000 3-inch squares of gold leaf to sticky copper plates that were then laid on the building’s dome. “The work is as much an art as a science due to how thin and fragile the gold leaf really is,” Doug Platt, communications manager for the state’s Department of Personnel and Administration, tells Mental Floss.

10 Facts About the Element Lead

iStock.com/aeduard
iStock.com/aeduard

Lead (Pb) is one of the most infamous elements in the periodic table. Though it’s now widely known as the source of lead poisoning, humans have been using the heavy metal for thousands of years. It’s soft, has a relatively low melting point, is easy to shape, and doesn’t corrode much, making it incredibly useful. It’s also relatively abundant and easy to extract. But lead is so much more than just No. 82 on the periodic table. Here are 10 facts about the element lead.

1. The element lead is easy to extract.

One reason people have been using lead for so long is because it’s so easy to extract from galena, or lead sulfide. Thanks to lead’s low melting point of 621.4°F (compare that to the melting point of iron, 2800°F), all you have to do to smelt it is put the rocks in a fire, then extract the lead from the ashes once the fire burns out.

Galena is still one of the major modern sources of lead. Missouri, the biggest producer of lead in the U.S. (and home to the largest lead deposits in the world), designated galena as its official state mineral in 1967. Galena is also the state mineral of Wisconsin, where it has been mined since at least the 17th century. Several towns across the U.S. are named after the mineral as well, most notably Galena, Illinois, one of the centers of the American “Lead Rush” of the 19th century.

2. People have been using lead since prehistory.

The oldest smelted lead object ever found was discovered in a cave in Israel in 2012. Researchers have dated the wand-shaped tool—potentially a spindle whorl—to the late 4000s BCE, tracing its origins to lead ores in the Taurus mountains of what is now Turkey.

3. Lead poisoning can be fatal.

Lead has a fairly similar chemical structure to calcium. Both have two positively charged ions. Because of that, inside the body, the toxic metal can bind to the same proteins as the vital mineral. Over time, lead poisoning occurs as the element crowds out the minerals your body needs to function, including not just calcium, but iron, zinc, and other nutrients.

Lead can travel through the body in the same way that those minerals can, including passing through the brain-blood barrier and into the bones. As a result, exposure to lead—whether through paint, pipes, contaminated soil, or any other means—can be very dangerous, especially for children, for whom lead poisoning can cause learning disabilities, delayed growth, brain damage, coma, and death. Scientists believe there is no safe threshold for lead exposure.

4. Ancient Romans really loved lead.

Lead use reached new heights during the Roman Empire. Ancient Romans used lead to make cookware, water pipes, wine jugs, coins, and so much more. Lead acetate was even used as a sweetener, most often in wine. As a result of ingesting a little lead with every bite of food and sip of water or wine, modern researchers have argued that two-thirds of Roman emperors (as well as plenty of common folk) exhibited symptoms of lead poisoning. A 20th-century examination of the body of Pope Clement II, who died in 1047, showed that lead poisoning led to the religious leader’s sudden demise, too—though there’s still some speculation of whether he was poisoned by an enemy or if he simply drank too much lead-sweetened wine.

5. Lead is a very stable element.

Lead atoms are “doubly magic.” In physics, the numbers 2, 8, 20, 28, 50, 82, and 126 are considered “magic” because those numbers of protons or neutrons completely fill up the atomic nucleus. Lead has 126 neutrons and 82 protons—two magic numbers. As a result, lead isotopes are incredibly stable. Lead-208 is the heaviest stable atom.

6. Lead made car engines quieter—at a high cost.

It’s not surprising that we no longer add lead to gasoline (TIME magazine called it one of the world’s worst inventions back in 2010). But why was it ever there in the first place?

In 1921, a General Motors researcher discovered that adding tetraethyl lead to gasoline reduced “engine knock” in cars, when pockets of air and fuel explode in the wrong place and time in a combustion engine. In addition to producing a loud sound, it also damages the engine. While there were other available chemicals like ethanol and tellurium that could similarly provide the octane boost to reduce knocking, leaded gasoline was easier and cheaper to produce, and unlike tellurium, it didn't reek of garlic.

Unfortunately, it came at a high cost for the refinery workers that produced leaded gasoline (who many of whom were sickened, driven mad, and killed by their exposure to it) and the environment as a whole.

In the 1960s, geochemist Clair Patterson was trying to measure the exact age of the Earth when he discovered a shocking amount of lead contamination in his lab—and everything he tested, from his tap water to dust in the air to his skin and samples of his dandruff. As he continued to experiment, he discovered that lead levels in ocean water began to rise drastically around the same time that lead became a common gasoline additive. Every car on the road was belching lead straight into the atmosphere.

Patterson would later become the driving force in forcing the U.S. government to ban leaded gasoline. (You can read more about him in our feature, “The Most Important Scientist You’ve Never Heard Of.”)

7. Lead was used in paintings …

Historically, lead wasn’t just prized for being an easy-to-shape metal; it was also valued for its color. Though most of us know that lead was historically used in house paint (and still continues to hide in the walls of some homes today), it was also a popular ingredient in fine art for thousands of years.

Produced since antiquity, lead white (also known as Cremnitz white) was a favorite paint pigment of the Old Masters of the 17th and 18th centuries, including artists like Johannes Vermeer and Rembrandt van Rijn.

“For two millennia, white leads—basic lead carbonate and sulfate—were the only white pigments that could deliver moderately durable whiteness and brightness into a drab world of grays and earth colors," pigment experts Juergen H. Braun and John G. Dickinson wrote in the third edition of Applied Polymer Science: 21st Century in 2000. Like a number of other pigments prior to the advent of synthetic paints, its toxicity was general knowledge, but for many painters, the risk was worth it to achieve the color they wanted. You can still buy it today, but it has largely been replaced with the safer titanium white.

Lead white isn't the only lead paint lurking in many famous paintings from history. Dutch artists like Vermeer also favored lead tin yellow, which you can see in his masterpiece The Milkmaid.

8. … and in makeup.

During the 18th century, both men and women used white lead powder to achieve fashionably ghostly complexions, though it was known to be toxic. They powdered their hair with white lead powder, too. The dangerous trend caused eye inflammation, tooth rot, baldness, and eventually, death. To top it off, using lead powder made the skin blacken over time, so wearers needed to apply more and more of the powder to achieve their intended look. Queen Elizabeth I, who lost most of her teeth and much of her hair by the end of her life, reportedly was wearing a full inch of lead makeup on her face when she died. While her cause of death remains unclear, one popular theory holds that she was killed by blood poisoning from her longtime reliance on those lead-filled cosmetics.

Researchers have hypothesized that several other famous historical figures either suffered from or died from lead poisoning, including painters like Vincent van Gogh and Francisco Goya. In several cases, exhumations have proved this: A 2010 analysis of what are thought to be Caravaggio’s bones showed very high levels of lead (enough to drive him crazy, if not outright kill him) likely from his exposure to lead paint throughout his life. Hair and skull fragments believed to belong to Ludwig van Beethoven also show very high lead levels, potentially from the wine he drank.

9. Lead is a superconductor.

Which means that if it is cooled below a certain temperature, it loses all electric resistance. If you were to run a current through lead wire that has a temperature below 7.2K (-446.71°F), it would conduct that current perfectly without losing any energy to heat. A current running through a lead ring could continue flowing forever without an outside energy source.

Like other superconductors, lead is diamagnetic—it is repelled by magnetic fields.

10. On Venus, it snows lead.

Venus is the hottest planet in the solar system, with an average surface temperature of 867°F. That’s far above lead’s 621.4°F melting point. In 1995, scientists discovered what appeared to be metallic “snow” on the mountains of Venus—a planet too hot to have water ice. In 2004, researchers at Washington University in St. Louis discovered that Venusian “snow” was probably a mixture of lead sulfide and bismuth sulfide.

This “snow” forms because Venus’s high temperatures vaporize minerals on the planet’s surface, creating a kind of metallic mist that, when it reaches relatively cooler altitudes, condenses into metallic frost that falls on the planet’s tallest peaks.

How Cold Is It in Canada? Niagara Falls Has Frozen Over

Aaron Vincent Elkaim, Getty Images
Aaron Vincent Elkaim, Getty Images

The cold snap that's gripped the northeast in an icy, subzero chill has made it hard to roll down frozen car windows and navigate roads. Elsewhere, it's having a significantly more spectacular effect: The roaring cascade of water at Niagara Falls at the United States/Canada border has slowed and even come to a stop in some areas, having effectively frozen over.

CNN reports that extreme temperatures have arrested the famous waterfall in spots, creating a kind of winter wonderland that some observers have compared to the handiwork of Elsa in Disney's Frozen. Here's what a similar scene looked like in 2015:

Visitors observe frozen areas of Niagara Falls in 2015
Aaron Vincent Elkaim, Getty Images

And here's a look at footage captured in 2019:

While covered by a sheet of ice, the Falls are not frozen solid: The volume and force of water prevents that. In the 1960s, steel ice booms were added to prevent large blocks from forming farther up the river that could slow the water enough to cause freezing. Instead, it's the surface water and mist that ices over, creating an aesthetically intriguing appearance. If it gets cold enough, ice can form as the water falls, leading to a large deposit on the bottom that can grow to over 40 feet thick.

It's rare for the Falls to come to a complete halt, but before the advent of the ice booms, it was a possibility. On March 30, 1848, gale force winds pushed ice floes from Lake Erie to the mouth of the Niagara River, creating a natural dam and effectively turning off the rushing water. People began walking over the dry riverbed and collected resurfaced weapons from the War of 1812; others thought it was a sign of the end of the world. Niagara Falls has never experienced a near-total interruption since.

[h/t CNN]

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