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What is Sand? (The Answer Will Surprise You.)

Curious World

We can put it in boxes to play in or bags to protect us from floods; when it shifts inside an hourglass, we use it to measure the days of our lives. Stone made of it can last for millennia, while castles made of sand only last a few days. It can be green, black, white, pink, or yellow. Yet few of us, if pressed, actually know what sand is.

With Sand, Size Matters

Most people think that sand is defined by what it’s made of, but it’s actually just a size. Geologists define sand as any granular mineral substance which a diameter between 1/16 of a millimeter to 2 millimeters. Sand grains are smaller than gravel, but larger than silt, in a continuum which goes from boulders all the way down to clay. Sand is nothing more than grains of rock which have been eroded down to extremely small size.

Famously, people have a love affair with sand. If questioned, most people wouldn’t say they are going to visit sand, yet sand is the main attraction of all the beaches, dunes and deserts of the world. We take trips to sit on it and read trashy novels. At home, we buy it for children to play in.

After traveling the world for 11 years, I’ve had the pleasure of visiting many sand-themed sites, many of which are among the greatest attractions in the world. Read on, the following are some of my favorite sands on the planet.

Namib Sand Sea, Namibia

Namibia is the second-least densely populated country in the world, and most of that space is taken up with sand. An enormous sea of sand with some of the highest sand dunes in the world.

I spent five days driving in the Namib Sand Sea, one of the most incredible experiences of my life. Especially noteworthy is the Langewall, or Wall of Death. It is a giant 100m (300ft) sand dune that runs along the length of the Atlantic coast.

We camped on top of it and drove straight down the dune to the coast in an off-road vehicle.

White Sands National Monument, New Mexico

Many places have white sand, but they are usually made of silica or calcium carbonate. At White Sands National Monument, the sand is actually tiny grains of gypsum, the same substance you probably have a few feet from you right now in the dry wall of your building.

This gypsum sand makes for an incredibly stark contrast between the white dunes and the blue sky.

Green Sand Beach, Hawaii

Sand can come in many colors, but there are few places on Earth where you can find green sand. The green sand beach in Hawaii is hard to find as there are no signs or roads which will take you directly there.

Located just a mile from the southernmost point of the Big Island of Hawaii (and subsequently the United States) the Green Sand Beach is the remains of a cinder cone where all of the ash eroded away.

The green comes from the mineral olivine, which is actually one of the most common minerals in earth’s mantle. It’s pretty, but doesn’t last long on the surface, geologically speaking. Olivine’s gemstone pieces are known as peridot.

Fraser Island, Australia

Fraser Island is the largest sand island in the world, and a major tourist attraction in Queensland. Located on the eastern seaboard of Australia, it is the result of millions of years of sand grain transportation by waves along the Australian coast – and now has incredibly wide beaches, dunes and wrecked ships to explore.

Great Sand Dune National Park, Colorado

Many people are surprised to find that there is a giant sand dune in the middle of the Rocky Mountains. Nonetheless, there is a massive pile of sand which has accumulated over time which rests up against the mountains.

Unlike the sand on Fraser Island which was transported by water, here the sand was transported by air (aeolian transportation). The dunes reach over 750 feet in height, making them the largest in the USA. Go in shoulder seasons. Summer temperatures have reached as high as 150F/66C.

Kobuk Valley National Park, Alaska

Even more shocking than dunes in the Rocky Mountains are sand dunes above the Arctic Circle. Kobuk Valley not only has the northernmost sand dunes in the world, it is also the least visited national park in the United States.

There are no roads, facilities, trails or signs anywhere in the park, and the only way to visit is via float plane. Like in Great Sand Dunes National Park, the temperature on the dunes here can get quite high, with summer temperatures breaking 100F.

Gary Arndt is an award-winning travel photographer and podcaster who sold his home in 2007 to roam the world nonstop, visiting 195 countries. He still travels, but now hangs his hat in Minneapolis. Photos of each destination listed here were taken by Gary. See more of his works at