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What is sand made of? And other fascinating sandy facts

BY Emily Goodman

17th Aug 2023 Life

What is sand made of? And other fascinating sandy facts

We delve into record-breaking sand contests, what happens when lightning strikes sand, whether quicksand is actually dangerous, and other burning sand questions

1. The rainbow colours of sand

You might think of all sand as boring beige. But sand comes in every colour. The black sand in Hawaii and Santorini has volcanic minerals mixed into it. Bermuda’s pink beaches get their colour from the red and pink shells of tiny marine creatures.

Even rarer is green sand; its colour comes from the mineral olivine. Only a few beaches have enough of it to appear green, one of which is in Norway.

And on Rainbow Beach in Australia, the sand ­appears in more than 70 colours.

2. Edible sand

Some of the things we consume are considered to be sand. We think of sand as the stuff that beaches are made of, but technically it’s any material made up of grains measuring six one-hundredths of a millimetre to two millimetres in diameter. According to that definition, salt and sugar qualify.

3. Parrotfish poop

Parrotfish feeding on rock on seabedParrotfish feed on dead coral, which they then digest and turn into sand

The stuff on the shores can come from a variety of sources, including from the poop of parrotfish, which eat algae and dead coral and excrete hundreds of tonnes of sand a year.

Sound gross? Perhaps, but the sand that comes out of parrotfish is what you’ll find on some of Hawaii’s most beautiful white beaches.

4. The uses of sand

Still, most sand comes from granulated rocks that streams carry to the sea—some 2 billion metric tonnes of it each year.

Yet we use 45 billion metric tonnes of sand around the world annually, to make sandpaper, paint and the silicon chips that power computers. It’s also in construction materials such as concrete, brick and glass.

5. Turning sand into glass

Fulgurite in sand created by lightning strikeCredit: Ji-Elle, CC BY-SA 3.0, via Wikimedia Commons. When lightning strikes sand, it creates glassy fulgurites

Depending on what’s in it, sand must be heated to more than 1,700°C to become glass.

The oldest (and fastest) glassmaker is lightning. When a bolt strikes dry sand, it instantly melts and fuses the sand into hollow branching glass tubes called fulgurites.

6. Sand's growing value

Not all sand is suitable for building. Desert sand is too smooth for the grains to lock together. Saudi Arabia, with all of its desert, has to ­import sand in order to build its cities.

With much of the world ­urbanising, the demand for sand has skyrocketed. Sand extraction is a billion-dollar ­industry worldwide.

7. Sand theft

People steal sand; there’s even a sand mafia in India. It’s illegal to take sand from any beach in ­Hawaii, though many tourists still do. Swiping sand from the Italian island of Sardinia could land you in prison.

8. A sandy habitat

When you lie on the beach, you’re lounging on someone’s living room. Though most of the creatures that make their homes in sand are ­microscopic, there are as many as a million of them in just one square metre of the stuff.

Meanwhile, larger animals such as sea turtles lay their eggs in sand. Not all of them hatch, and those that don’t hatch provide nutrients for the plant life that grows in the dunes.

9. Record-breaking sand dunes

Peru's Cerro Blanco sand duneCredit: Medhus, CC BY 2.0, via Flickr. Peru's Cerro Blanco is among the tallest sand dunes in the world

Some of the world’s biggest, most breathtaking sand dunes are found in South America. The Duna Federico Kirbus in Catamarca, Argentina, is the world’s tallest dune, measuring a mountain-like 1,234 metres high (2,845 metres above sea level).

Just slightly smaller in stature is Peru’s Cerro Blanco at 1,176 metres high. The country’s vast sand dune fields make it a popular destination for sports like sandboarding and dune buggy driving.

10. Sinking sand

But be ­careful. Sand—on a dune, in the desert, or at the beach—can shift quickly. Sandbars are especially dangerous. They can be submerged in a matter of minutes, and riptides often form in breaks in the bar.

As for quicksand, it’s not as deadly as films might have you believe. If you do find yourself stuck, lean back to distribute your weight over a larger area.

11. Sand castles in the sky

The world’s tallest sand­castle was built in July 2021 at the annual sand-sculpting festival held in Blokhus, Denmark.

Led by Dutch artist Wilfred Stijger, a team of 30 sand sculptors constructed the castle using 4,860 tonnes of sand, mixed with a bit of clay for stability. Its tallest peak stands at 21.16 metres—three metres taller than the previous record-holder, built in 2019 in Binz, Germany.

12. Enter Sandman

German writer ETA Hoffmann’s 1816 short story “Der Sandmann” popularised the myth about a creature who sprinkles sand in our eyes while we sleep.

One version of this folk tale is that the sand ­induces sweet dreams—hence the lyrics of a 1954 song made famous by The Chordettes: “Mr Sandman, bring me a dream...”

13. Counting sand

It’s been said there are more stars in the universe than grains of sand on the world’s beaches.

Of course, neither can be literally counted. But researchers at the University of Hawaii estimated the number of grains of sand on earth: 7 and a half quintillion (that’s 75 followed by 17 zeros).

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