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  • Sand, whether you use it for building sand castles, telling time with an hourglass, or

  • hydraulic fracturing, is pretty much the same just about anywhere you go -- an uncountable

  • number of tiny grains mixed together to form the same dunes and beaches.

  • But why does sand almost always look the same? And how does so much of it end up at the beach?

  • Well, much of the world's sand is made out of the same stuff-- tiny crystals of the mineral

  • quartz, which is made out of silicon and oxygen, the two most common elements in Earth's crust.

  • And as you'll know if you've ever bitten through the crust -- of a sandwich -- that had sand

  • in it -- quartz grains are small, and really tough. Here's why:

  • Quartz crystals form within a cooling blob of molten granite rock, or magma, deep under

  • Earth's surface. As the magma cools, different minerals crystallize into solid rock at different

  • temperatures, and quartz is one of the last minerals to form. It's forced to crystallize

  • in the tiny spaces left in the now cooling rock, pretty much ensuring that it ends up

  • in a specific size range.

  • But being last has lasting advantages. Minerals that do form in the earlier, hotter conditions

  • have weaker chemical structures and weather away more easily than quartz, kind of like

  • how a relationship forged in the heat of passion might not be as stable as a deep bond developed

  • over time. So as the weak, flash-in-the-pan minerals wear away, the unfaltering quartz

  • grains are left to pop out of the rock as sand!

  • And then it's only a matter of time--sometimes a very long time-- before the quartz sand

  • gets whisked away by streams and rivers and carried to the sea. There, at the mouth of

  • a river, the fast-flowing water slows abruptly, and the well-rounded sand drops out. Larger

  • rocks and pebbles were already left behind upstream, while smaller sediments like silt

  • and clay continue to be swept along by the weakened current and are deposited further

  • from shore.

  • Over thousands and thousands of years, the paths of rivers sweep up and down the coast,

  • dropping off piles of sand to be spread by waves and currents into smooth sandy beaches.

  • Of course, not all beaches are purely quartz sand, and not all quartz sand ends up on beaches

  • - but the fact that so many beaches and so many sands are the same is a testament to

  • the chemistry of the most common components of earth's crust as they cool and crystallize,

  • and to the physics of sediments slowly shifting and surging towards the sea. They are, quite

  • literally, the real sands of time.

Sand, whether you use it for building sand castles, telling time with an hourglass, or

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