20. Calcium: Stone and Bone

Stories of turning flesh to stone — and vice versa — are common in mythology. With calcium, we see how those same transitions can happen in the real world.

Featured above: Shakespeare Cliff in Dover, England, so named directly because of its association with King Lear.

Show Notes

Podiatric Pedantry: I referenced a certain eight-legged marine animal in the plural as “octopuses,” and I just want to cut off any hypercorrective dogmatists by saying yes, that is correct, and if you want to be extremely technical, “octopi” is actually an etymological abomination. As the OED says:

Although it is often supposed that octopi is the ‘correct’ plural of octopus, and it has been in use for longer than the usual Anglicized plural octopuses, it in fact originates as an error. Octopus is not a simple Latin word of the second declension, but a Latinized form of the Greek word oktopous, and its ‘correct’ plural would logically be octopodes.”

Of course, this podcast is on the record as being strictly anti-prescriptivist, so I’m only addressing the most offensive of word nerds here. “Octopi” is commonly understood to mean “several octopuses,” and is thus perfectly acceptable. “Octopodes,” meanwhile, is commonly understood to mean “I’ve taken my grammar fetish way too far,” and should be avoided in mixed company.

“Winning” A Bet: Our friend Pliny the Elder recounts a colorful tale about this white element in Naturalis Historia. Cleopatra, Queen of Egypt, sought to impress the Roman politician Marc Antony and wagered that she could throw the most expensive banquet ever given.

Sufficiently intrigued, Antony agreed. The next day, she set before him a meal that was indeed luxurious, but the most expensive banquet in history? Antony thought not.

Cleopatra smiled and silently removed one of her earrings. It was made of an enormous pearl, worth tens of millions of dollars by modern estimations. She dropped it into a glass of vinegar, and with an effervescent fizz, the pearl dissolved in the glass.

She drank the entire thing, and Antony, gobsmacked, knew he had lost the bet, because he was a simpering fool. He should have known better than to engage in an apocryphal battle of wits against Cleopatra.

So Simple A Beginning: In 1868, Thomas Henry Huxley (AKA “Darwin’s Bulldog”) gave a lecture entitled, “On A Piece Of Chalk.” It walked the audience through the entire geological history of England, starting with the famous white rocks of Dover.

It’s often held up as a masterpiece of popular science, being one of the first works of scientific expertise that was intended for a general audience. It’s not quite as clear to the modern reader, but can be read in its entirety online.

I’ve Made A Terrible Mistake: I can almost understand someone performing electrolysis on milk out of curiosity, if they don’t know what to expect. But I’ve watched this video, and I am here to tell you: You shouldn’t. This is disgusting. It’s pretty much like the VHS tape in The Ring and I think now I only have seven days to live.

If that doesn’t deter you, here you go:

Episode Script

An Indonesian myth tells the cautionary tale of Malin Kundang, a young man from a poor family that lived by the sea. One day, he saw a merchant ship getting attacked by pirates, and heroically helped fight them off. The ship’s captain was so grateful that he allowed Malin Kundang to join his crew.

After several years, he became a wealthy man. When he returned home, he was embarrassed by the sight of his own mother, who was covered in rags and dirt. He denied having ever known her, and she cursed him. He turned to stone on the beaches of Air Manis, where Batu Malin Kundang remains to this day.

In Greek legend, Pygmalion was a sculptor so talented that he fell in love with his own statue. Aphrodite, goddess of love, took pity on him and turned the ivory carving into a real woman of flesh and blood.

Stories like this can be found across all cultures and all times. The human imagination seems to be riveted by the idea that our vibrant bodies, full of blood and air, could be turned into something as timeless and lifeless as rock. Or vice versa.

But the transformation of life to rocks and back again does not occur only in the realm of myths and legends. Even in our world of mere mortals, the boundary between stone and bone is made quite blurry by Element 20, calcium.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re seeing just how much good calcium does a body.

You’ve probably heard that you’re not allowed to yell “Fire!” in a crowded theater if there isn’t actually a fire. Hopefully this is not an idea that would normally occur to you, because you’re probably not some kind of mischievous imp. But you might also wonder, who expects a fire to break out in a theater? Is that a thing that happens?

In short, yes. Somewhere between one and two dozen theaters go up in smoke every year around the world.1 2But it is nowhere near as common a phenomenon as it used to be. In the 18th and 19th centuries, stages were lit by flame. A series of gas-fueled footlights at the front of the stage would illuminate the performers. All it would take was a stray bit of fabric or frayed rope to start a fire that would bring the house down.

The theater-going experience was made much safer over the course of the 1800s, when Scottish scientists discovered something interesting about calcium oxide, sometimes called quicklime: When exposed to a flame fueled by hydrogen and oxygen gases, it burned almost as brightly as the sun.

This light could be housed in a cylinder at the back of the theater and light the entire stage, keeping the dangerous bits far away from any clumsy actors.

Thanks to a few Scottish scientists and calcium, an evening at the theater became a relatively safe experience. And after centuries of performance, actors could finally step into the limelight.



One performance that has played out countless times on stages both flammable and fireproof is Shakespeare’s King Lear. In Act IV, Scene I, the blind and desperate Earl of Gloucester laments,

There is a cliff, whose high and bending head
Looks fearfully in the confined deep.
Bring me but to the very brim of it,
And I’ll repair the misery thou dost bear
With something rich about me. From that place
I shall no leading need.

Here Gloucester is referring to the Cliffs of Dover, the jagged feature of Britain’s southeast coast that’s famously bone-white. That’s thanks to calcium-rich deposits of… well, bone.

Seventy million years ago, that part of the world was covered by a vast sea, where a kind of life called the coccolithophore flourished. These are single-celled algae covered in bony plates of calcium carbonate. When they died, they would sink to the sea floor, where those calciferous corpses would accumulate, slowly, very slowly. About half a millimeter per year, until they piled up 500 meters deep. There, under their own weight, they were pressed into sheets of chalk.

As tectonic plates shifted over time, those sheets were pushed above the waters to form the cliffs we see today. They provide surprisingly fertile ground for grass and flowers, where bluebirds flock and ponies graze, incorporating that mineral into their own bodies.

From bone to stone and back again, the White Cliffs of Dover provide one of the most beautiful conjunctions of geology and biology anywhere in the world.

Element 20 might be the mineral that’s most famous for crossing the line between those disciplines, being as renowned for its inorganic forms, like lime, chalk, marble, and alabaster, as it is for living materials like ivory, pearls, and especially bones. What’s ironic is that none of those have much to do with the most critical function calcium plays for all life on Earth.

See, you don’t actually need bones to live. Well, you probably do. Please don’t do anything rash. But there are innumerable animals that get along just fine with no bones at all, like spiders, octopuses, worms, and jellies, not to mention microscopic animals and bacteria, or plants and fungi. And yet, all of those life forms require calcium if they want to stay alive.

Calcium’s most important biological role is as a component of cellular signaling. Biological cells need to communicate somehow, in order to know when, for example, to twitch a muscle, or when to release saliva. Calcium is the universal medium by which cells send many of those signals.

In the same way that potassium is critical for all nerve function, and phosphorus is used as a way for cells to store and release energy, calcium performs an equally crucial role as a messenger in biochemistry.

This is so important that early in the history of life on earth, some organisms started to keep a special reserve of calcium for lean times. Those organisms often had a better chance of survival than those that didn’t. So after a particularly calcium-rich meal, some early animal might have tucked away extra stores of element 20 in some otherwise unused space. Since calcium is a solid, these stores would naturally become rigid and strong.

This is thought to be the evolutionary origin of bone: a storehouse for hard times. The fact that those extra supplies could double as a biological framework or armor was merely a side effect. Granted, it’s a very beneficial side effect.

But something incredible happens when we work calcium with our hands to create something new, a synthetic material that has the characteristics of stone, but has been bent and molded according to our will.

When limestone, clay, shale, and sand are mixed with water into a slurry, the blend hardens into one of the most widespread materials in human history: Concrete.

Concrete might not be a newly discovered material, like the carbon nanotube, or highly fashionable, like textiles can be, but it can be sculpted into just about any shape and is structurally sound enough to support entire civilizations. It plays an obvious utilitarian role in modern transportation, from bridges to parking garages to the very roads themselves, but also more generally, as the foundation of almost every kind of infrastructure.

But for as widespread as concrete is in the 21st century, the ancient version of this technology was actually far superior.

That might sound kind of outrageous. We have smartphones, after all, and jet engines, and sous-vide machines and gene sequencing and podcasts! How is it possible that anything we have today is worse than it was thousands of years ago?

Well, the proof of a material is in its longevity. Structures built with modern concrete usually have a lifetime of around 50 or maybe 100 years. This has been made especially clear in the United States by the sheer number of crumbling concrete bridges, constructed in the mid-20th century and now approaching the ends of their lives.

And yet, curiously, there are concrete structures built thousands of years ago that are still standing today. A particularly notable example is the Pantheon in Rome, a temple that boasts the title of “Largest Unreinforced Concrete Dome in the World,” and has held that title since 126 CE.

The concrete made by ancient Romans was the strongest in the world, because they cleverly took advantage of a chemical reaction they had seen happen naturally around volcanoes.

Most concrete consists of aggregate, large stones and sand, that’s held together by cement, which acts like a glue.3 4The aggregate is completely inert, so that it doesn’t cause cracks and make the structure crumble.

With Roman concrete, the aggregate was reactive, but in a very special way. Rather than expanding and cracking, it would actually bond with the cement, forming a stronger bond material.5 6This change makes all the difference. Even piers that have been battered by waves for millennia still stand today because they were built with Roman concrete, while your city’s roads need to be repaved every third year.7

The roads built by Rome spanned hundreds of thousands of miles across dozens of disparate cultures, much of it paved with concrete. Overhead, concrete aqueducts kept cities supplied with clean water, were an enormous symbol of civic pride, and still stand in some places today.

Alas, the required recipe for such a wonder material was quite precise, and lost over time. No surviving record has been found, so unlocking the secret of Roman concrete has been a painstaking exercise in reverse-engineering.

Only by using modern technologies like chemical analysis, X-ray microdiffraction, and electron microscopy have we even begun to rediscover the precise technology that was so widespread two thousand years ago.8

But human artisans do more with element 20 than pour it into molds. With chisel in hand, the most skilled are able to turn a block of stone into the ideal human form.

There is no shortage of beautiful statues in the world, but coincidentally, perhaps the finest masterpiece of marble sculpture in the world is also an Italian creation.

On September 13, 1501, a 26-year-old sculptor began studying an enormous slab of Carrara marble — his newest problem to solve. He had not chosen this particular stone for the project. In fact, two other renowned sculptors had tried their hand at this very commission before abandoning it because the marble was of such poor quality. For as long as this artist had been alive, the block had lain neglected in the church courtyard, subjected to decades of wind, sun, and rain, too inferior to use, yet too expensive to discard.9

But Michelangelo was going to succeed where others had failed. Not only would he transform this block of unwanted stone into a statue of the Old Testament figure David, he would do so with such unparalleled skill that one contemporary art critic said that he had brought the dead back to life, and one never need see another sculpture for as long as they lived.10

Towering 17 feet tall, David is a depiction of the Jewish leader as a young man, in the moments before his battle with the Philistine giant Goliath. He’s presented with a mix of terror and determination in his eyes, inhabiting a nude body that exemplified the ideal male physique.

So highly regarded was Michelangelo’s piece that it was not placed on the roof of the Florence Cathedral, as originally intended, but in a public square, where all eyes could admire the sculptor’s work.11

Since then it’s been moved indoors, but David is still seen by over 8 million visitors a year at the Galleria dell’Accademia in Florence, visitors who travel from around the world to see, embodied in calciferous form, an idealized version of their own anatomy.

Tourists have ogled the specimen for centuries, and while none of them can hope to outlive David, no one lives forever — and all those viewers are actually helping to hasten the demise of this man of stone.

As a visitor walks around the statue of David, their footfalls cause tiny vibrations, which travel across the floor and up through the statue. These , but considering we’re talking about 16 million feet per year making hundreds of steps each, that really adds up. If it’s not insulated from those vibrations, the mighty David could eventually be toppled by those much smaller than he.12

So far, we’ve discussed the transformation of stone to flesh in rather poetic terms, which I hope you’ll agree is reasonable: Aphrodite hasn’t brought any statues to life since Pygmalion’s, after all.

But when traveling in the opposite direction, we run into the opposite issue. The transmogrification of flesh to stone is horrific, and heartless, and a phenomenon that is very, very real.

Harry Raymond Eastlack, Jr., could tell you that much. In 1935, as a five-year-old, Eastlack broke his leg while playing with his sister. The fracture was a little messy, and it didn’t set properly. He started feeling some stiffness in his knee and his hip. Before long, that pain started to spread.13

The problem wasn’t that the fracture wouldn’t heal; if anything, it was that Eastlack’s body was trying to heal too much. So enthusiastically that it was converting the muscles and tendons in his leg into bone.14

Eastlack was one of the few hundred people around the world who lived with a genetic disorder called fibrodysplasia ossificans progressiva, or FOP. It typically kicks in around adolescence, but breaking a bone at a young age got things off to an early start for Eastlack. At that point, there wasn’t much that could be done for him.15

Doctors tried to surgically remove these bone growths, but that only spurred his body into “healing” the area with more new bone, even thicker than before.

By his mid-twenties, Eastlack’s spine had begun to fuse into one piece. Many of his back muscles had coalesced as bone, forming a sort of skeletal shell around his torso. In his late thirties, the condition covered most of his body, even his jaw, leaving him only able to move his lips.

He died of pneumonia only a few days before his 40th birthday.

But Eastlack still gets around, and he’s actually pretty popular.

Shortly before he died, he donated his body to science, and he now spends his days in a glass case at the College of Physicians of Philadelphia. He’s not quite Otzi the Iceman, but Eastlack’s body has been subject to a lot of study. In 1995, his remains were even brought to a two-day conference of orthopedic surgeons, geneticists, molecular biologists, and people living with FOP and their families.

To this day, there is no cure for FOP. But thanks in large part to Eastlack’s generous gift to science, doctors have learned a lot about treating the condition. It’s not in itself fatal, and modern medical treatments can sometimes help patients live to an older age than Harry Eastlack did.

Fibrodysplasia ossificans progressiva offers us a reminder, albeit a stark one. Our bones provide the important scaffolding upon which the rest of our bodies hang, but although that scaffolding is hard as a rock, it moves. It grows. It is very much alive.

How fitting that is for the part of our anatomy most closely associated with calcium, the chemical element that is equal parts geological and biological.

We element collectors can afford to be a little less selective than master sculptors, so now might be a good time to ask your artist friends and local churches if they have any really disappointing blocks of marble just lying around.

If that doesn’t work out, no worries. Calcium is highly abundant on Earth, so we have plenty of backup options to choose from.

You might have noticed that most of these calcium compounds have something in common: They’re characteristically white. In fact, calcium is such a reliable source of whiteness that, for quite some time, it was the key ingredient in a kind of paint called whitewash.

It was used very widely — you’ve definitely seen at least one famously whitewashed building. Originally painted in 1798, the Executive Mansion became so inexorably linked with its color that in 1901, President Theodore Roosevelt officially renamed it the White House.16

That location would make a poor source for calcium collection, unfortunately. Modern white paints don’t depend on lime to create bright whites, and besides, you would almost certainly be enthusiastically dissuaded from such an endeavor by the Secret Service.

Unlike bananas’ claim to potassium, you actually can believe the hype around milk: One cup of milk provides about one third of an adult’s daily requirement of calcium. Unfortunately, it tends to be an even better source of sugar. Skim milk is, by that metric, actually the worst kind you can drink. Since all that delicious fat has been removed, that’s the kind that tends to get the most sugar added.

And as far as our collections go, milk is not very helpful. It would be pretty difficult to extract the 300 milligrams present in one cup. There are actually people on the internet who have tried running a high voltage electrical current through a glass of milk, Humphry Davy-style, but even if that worked, it would not be worth the disgusting mess you’d have on your hands.

Much better, then, to stick with an inorganic source, like a piece of chalk — or, at the very least, an organic source that’s been dead for quite some time.

If you were so inspired, you could actually start a whole new sub-collection of seashells, bones, and coral. All of them are rich and lovely sources of calcium, and could really add a new dimension to your stockpile.

I might be over-complicating this whole thing, though. If the mere thought of all this work is giving you a bit of heartburn, please do feel free to grab an antacid tablet. And while you’re at it, store one away for safe keeping: Those medicines, which work by making the stomach a little less acidic, are usually a cheap, easily accessible source of calcium.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To see videos of modern-day mad scientists performing electrolysis on milk, and learn how calcium is responsible for the world’s most expensive banquet, visit episodic table dot com slash ca.

Next time, we’ll uncover the shocking secrets behind scandium.

This is T. R. Appleton, reminding you that calcium is technically a metal, so you have more in common with Wolverine than you might have thought.


  1. Top Of Show, Theatre Fires Are Not Something That “Used To Happen.” Patrick Hudson, December 31, 2013.
  2. Top Of Show, Theatre Fires Aren’t A Thing Of The Past. Patrick Hudson, December 31, 2014.
  3. Concrete Contractors Association Of Greater Chicago, What’s The Difference Between Cement And Concrete?
  4. Portland Cement Association, How Cement Is Made.
  5. The Independent, Mystery Of 2,000-Year-Old Roman Concrete Solved By Scientists. Harriet Agerholm, July 4, 2017.
  6. History.com, The Secrets Of Ancient Roman Concrete. Sarah Pruitt, June 21, 2013.
  7. The Telegraph, Secret Of How Roman Concrete Survived Tidal Battering For 2,000 Years Revealed. Sarah Knapton, July 3, 2017.
  8. Science Alert, Why 2,000-Year-Old Roman Concrete Is So Much Better Than What We Produce Today. Signe Dean, July 4, 2017.
  9. Encyclopedia Britannica, How A Rejected Block Of Marble Became The World’s Most Famous Statue.
  10. The New York Times, Who Owns Michelangelo’s ‘David’? Elisabetta Povoledo, August 31, 2010.
  11. Encyclopedia Britannica, David. Last updated January 28, 2009.
  12. BBC News, Michelangelo’s David ‘May Crack’. Mark Duff, September 19, 2008.
  13. The New York Times, Bone, A Masterpiece Of Elastic Strength. Natalie Angier, April 27, 2009.
  14. U.S. National Library of Medicine, Fibrodysplasia Ossificans Progressiva.
  15. The Atlantic, A Few Hundred People Turned To Bone. Thomas Maeder, February 1998.
  16. The White House Historical Association, Why Is The White House White?

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