Arlyn Greenebaum, age 12,

What exactly is sand?

The white sands of New Mexico are powdered  gypsum, spread out by some complex chemical reaction in the ground. Golden sands and yellow sands are made mostly from the mineral quartz. Tiny crystals of quartz often form as seething lava cools into solid rock. They become embedded in masses of rock such as granite,

Time and weather wear away bedrock, but the little crystals of quartz are hard enough to resist. As the bedrock disappears, they are freed from prison. Billions and countless billions of them are freed as the pounding surf wears down the coastal rocks,. These little crystals of quartz form the yellow sand on the seashore.