Mosaic

 

I’ve always just assumed that sand is sand; the exact same stuff no matter where on earth you find it. But I was wrong. Some months ago, I read an article about the construction boom in Asia, and how beaches and sea beds are being depleted for the sand used in concrete. I thought, “That’s just dumb. Why don’t they just use sand from the desert? The Gobi is the world’s fifth largest desert; no further away than some of the beaches they’re plundering. And who would miss the sand there?” But desert sand is created by wind, not waves. It tends to be much finer than ocean sand, and therefore useless in making concrete. It isn’t even made of the same stuff. Desert sand is mainly gypsum, feldspar and muscovite. Oceanic sand is much higher in silica – natural glass – along with tiny bits of coral and sea shells.