10 Quick Facts About Cobalt

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How well do you know the periodic table? Our series The Elements explores the fundamental building blocks of the observable universe—and their relevance to your life—one by one.

Cobalt hides out in everyday objects and happenings around us, from batteries and blue paint to medical procedures. We've used it for millennia, even before the common era, but it didn't get proper credit until the 18th century. With its 27 protons, cobalt is sandwiched between iron and nickel in the middle portion of the periodic table with the other "transition" metals, which bridge the main group elements located on either side. Here are ten curious facts about this element.

1. PURE COBALT DOES NOT NATURALLY EXIST ON EARTH.

Though you can find cobalt just about everywhere—in the soil, in mineral deposits, and even in crusts on the seafloor—it's always combined with other elements like nickel, copper, iron, or arsenic, such as in the bright crimson arsenate mineral erythrite. It's usually collected as a byproduct of mining for other metals—especially nickel and copper—and, once purified, is a burnished gray color.

2. COBALT MAY NOT BE RARE, BUT IT IS VALUABLE.

Despite being relatively common, it's considered a critical raw material by the European Union because there are few places where it's abundant enough to be mined in larger quantities. The only mine in the world where it's the primary product is in Morocco.

3. COBALT WAS NAMED AFTER SUBTERRANEAN GERMAN GOBLINS.

Centuries ago, miners in the mountains of Germany had a great deal of trouble trying to melt down certain ores for useful metals like silver and copper, and even dealt with poisonous fumes released from the rock, which could make them very sick or even kill them. They blamed the kobolds—pesky, underground sprites of local folklore (and more recently, the name of a Dungeons & Dragons species). Though the vapors actually arose from the arsenic also contained in the ores, when chemists later extracted cobalt from these minerals, the name stuck.

4. COBALT WAS FINALLY ISOLATED IN THE 18TH CENTURY.

It was not until the 1730s that Swedish chemist George Brandt purified and identified cobalt from arsenic-containing ores, then another 50 years until Torbern Bergman, another Swede, verified Brandt's new element. It is worth noting, though, that at the time the elements were simply in an incomplete list and had not been organized into a meaningful table.

5. COBALT IS BEST KNOWN FOR CREATING A RICH BLUE HUE…

People have been using cobalt-containing pigments to get that rich blue hue as far back as the 3rd millennium BCE, when Persians used them to color their necklace beads. From Egypt to China, artisans created blue glass from cobalt compounds for thousands of years. The color was long attributed to the element bismuth, depriving cobalt of pigment fame. 

6. … BUT COBALT MAKES OTHER COLORS TOO.

The famed "cobalt blue" is actually the result of the compound cobalt aluminate. Cobalt in other chemical combinations can also make a variety of other colors. Cobalt phosphate is used to make a violet pigment, and cobalt green is achieved by combining cobalt oxides with zinc oxides.

7. TODAY WE USE COBALT TO MAKE POWERFUL MAGNETS AND "SUPERALLOYS."

Cobalt is one of the few elements that are ferromagnetic, which means it can become magnetized when exposed to an external magnetic field. Cobalt remains magnetic at extremely high temperatures, making it very useful for the specialized magnets in generators and hard drives. When mixed with the right metals, cobalt can also help create materials called "superalloys" that keep their strength under huge stress and high temperatures—advantageous, for instance, in a jet engine. Most people, however, can find cobalt hiding closer to home, inside some rechargeable batteries.

8. COBALT COULD ONE DAY REPLACE PRECIOUS METALS IN INDUSTRY.

Scientists such as chemist Patrick Holland at Yale University are looking at ways to use cobalt in place of the more rare and expensive metals often used in industrial catalysts. These catalysts—chemical "helpers" that speed up reactions—are used in making adhesives, lubricants, or pharmaceutical precursors, for instance. Precious metals like platinum and iridium often make good catalysts, but they are also pricey, can be toxic to humans, and, as precious implies, are not abundant. There is a "big upswing in people looking at iron, nickel, and cobalt because of their price," Holland tells Mental Floss.

All three could be viable options in the future. The challenge, Holland says, is "walking the tightrope" between creating an effective, reactive catalyst and one that is too reactive or overly sensitive to impurities.

9. COBALT HAS MULTIPLE ROLES IN MODERN MEDICINE.

The metal perches in the middle of the impressively complex molecule vitamin B12—a.k.a. cobalamin—which is involved in making red blood cells and DNA, and helps keep your nervous system healthy. Cobalt also lends an extra distinction to B12: It's the only vitamin that contains a metal atom.

To measure B12 intake in patients, doctors use a "labeled" version of B12 in which the cobalt atom is replaced with a radioactive cobalt isotope. Oncologists and technicians also use the radiation from cobalt isotopes in some cancer therapies as well as to sterilize medical and surgical tools. These days, cobalt alloys are even found in artificial hip joints and knees.

10. COBALT WAS ONCE ADDED TO BEER—WITH DEADLY CONSEQUENCES.

In the 1960s, some breweries added cobalt chloride to their beers because it helped maintain the appealing foam that builds when beer is poured. By 1967, more than 100 heavy beer drinkers in Quebec City, Minneapolis, Omaha, and Belgium had suffered heart failure, and nearly half of them died. At the time, doctors were also administering cobalt to patients for medical reasons without causing this severe effect, so the blame couldn't lie with the metal alone. After studying the remains of the deceased, scientists proposed that the so-called "cobalt-beer cardiomyopathy" had been caused by an unhealthy mélange of cobalt, high alcohol intake, and poor diet. The FDA banned the use of cobalt chloride as a food additive shortly after. 

8 Facts About Silver

Peter Macdiarmid/Getty Images
Peter Macdiarmid/Getty Images

Subtle silver gets pushed aside next to gold, but in many ways it outranks its lustrous competition. The cool-toned element is more conductive and more reflective, and boasts properties absent in other metals, like a reaction with light that put the “silver” in “silver screen.” Read on for more.

1. HUMAN USE OF SILVER DATES BACK TO 3000 BCE.

Archeological records show humans have mined and used silver (or Ag, number 47 on the periodic table) for at least 5000 years. Silver shows up in slag heaps at ancient mines in Turkey and Greece, as well as in deposits in China, Korea, Japan, and South America. Its visible shine made it popular in jewelry, decorative objects, and practical tools like the aptly named silverware. Its rarity gave it high value. Silver coins are credited with fueling the rise of classical Athens, and Vikings used “hacksilver”—chunks of silver bullion chopped off a larger block of the metal—as money.

2. SOME INDIGENOUS CULTURES WERE EXPERTS AT SILVERSMITHING.

As a soft, pliable metal, silver is easily smelted, but the process still requires moderate heat. Metal workers in the precolonial Americas didn’t have bellows to pump oxygen to a fire; instead, several people would encircle the fire and blow on it through tubes to increase its intensity. The Inca of the Andes became expert silversmiths. They believed gold was the sweat of the sun, and silver came from the tears of the moon.

3. SILVER CONDUCTS ELECTRICITY BETTER THAN ANY OTHER METAL.

Of all metals, silver is the best conductor of heat and electricity, so it can be used in a wide variety of applications. Metal solder, electrical parts, printed circuit boards, and batteries have all be made with silver. But it’s expensive: In electrical wiring, copper is often used instead.

4. ITS REACTIVITY TO LIGHT MADE EARLY PHOTOGRAPHY POSSIBLE.

In the 1720s, German physicist Johann Heinrich Schulze produced the first images with silver. Having discovered that a piece of chalk dipped in silver nitrate would turn black when exposed to sunlight, Schulze affixed stencils to a glass jar filled with a mix of chalk and silver nitrate. When he brought the jar into the sun, the light “printed” the stencil letters onto the chalk. A century later, Louis-Jacques-Mandé Daguerre created photographic prints on silver-coated copper plates. At the same time, British chemist William Henry Fox Talbot devised a method for developing an exposed image on silver iodide-coated paper with gallic acid.

“The effect was seen as magical, a devilish art. But this mystical development of an invisible picture was a simple reduction reaction,” science reporter Victoria Gill explains on the Royal Society of Chemistry’s podcast Chemistry in its Element. “Hollywood could never have existed without the chemical reaction that gave celluloid film its ability to capture the stars and bring them to the aptly dubbed silver screen.” Silver salts are still used in rendering high-quality images.

5. THAT SAME REACTIVITY CAN ALSO CAUSE TARNISH.

Silver reacts with sulfur in the air, which forms a layer of tarnish that can darken or change the color of a silver object. The tarnish interferes with how silver reflects light, often turning the object black, gray, or a mix of purple, orange, and red. An at-home experiment can demonstrate the process: Put a shelled and quartered hard-boiled egg (preferably still warm) in the same container as a silver object, like a spoon, and seal the container closed. The tarnish should appear within an hour, thanks to the egg’s release of hydrogen sulfide gas, and grow darker as time goes on.

6. RESEARCHERS ARE STILL EXPLORING SILVER’S ANTIMICROBIAL PROPERTIES.

According to a 2009 review, silver was one of the most important anti-microbial tools in use before the discovery of modern antibiotics in the 1940s. The ancient Macedonians were likely the first to apply silver plates to surgical wounds, while doctors in World War I used silver to prevent infections when suturing battlefield injuries. Silver is toxic to bacteria, but not to humans—unless it’s consumed in large quantities. Ingesting too much silver can cause argyria, a condition where the skin permanently turns gray or blue due to silver’s reactivity with light.

A 2013 study in Science Transitional Medicine looked into the mechanisms behind silver’s anti-microbial powers. The findings suggested that silver makes bacterial cells more permeable and interferes with their metabolism. When antibiotics were administered with a small amount of silver, the drugs killed between 10 and 1000 times more bacteria than without it. “It’s not so much a silver bullet; more a silver spoon to help [bacteria] take their medicine,” lead researcher James Collins, a biomedical engineer at Boston University, told Nature.

7. SILVER IODIDE HELPS MAKE IT RAIN.

When regions need rain after a prolonged drought, scientists can “seed” clouds by spraying silver iodide particles into the atmosphere. In the 1940s, Bernard Vonnegut (brother of the author Kurt Vonnegut) demonstrated in a lab that silver iodide provides a scaffold on which water molecules can freeze, which (theoretically) would lead to precipitation in the form of snowflakes. In a 2018 study, researchers from the University of Colorado in Boulder and other institutions demonstrated the process in actual clouds. The team sent out two planes; one to spray silver iodide and the other to track its course and measure how water responded. The second plane recorded a zigzagged line of water particles freezing in the same flight path as the plane spraying silver, confirming silver iodide’s role in cloud seeding.

Bernard Vonnegut had made his discovery while he and his brother both worked for General Electric in Schenectady, New York. The two discussed the idea of water stabilized as ice at room temperature—a concept that Kurt Vonnegut went on to explore as ice-nine in his novel Cat’s Cradle.

8. SILVER IS RESPONSIBLE FOR A LOT OF GHOST TOWNS.

The United States established a “bimetallic” currency during George Washington’s presidency. The policy required the federal government to purchase millions of ounces of silver each year to mint coins or set the value of paper currency. Government demand for silver contributed to the boom of Western mining towns in the mid-19th century, encouraged by the 1890 Sherman Silver Purchase Act, which increased the federal purchase of silver.

But falling values in relation to gold eventually led to the repeal of the Sherman act, and the price of silver crashed. The mining settlements shrank from hundreds of residents to just a handful—and some were completely abandoned. Ghost towns (or minimally populated near-ghost towns) with names like Bullionville, El Dorado, Potosi, and Midas can still can be explored in Nevada, the Silver State.

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.

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