In honor of construction season, I offer an odd fact about a common building material. Well, not quite. As a politician might say, I misspoke. Actually, it's generated out of thick air-polluted air, to be precise. The chief ingredient of wallboard is gypsum, a mineral also known as calcium sulfate dihydrate.
Pure gypsum can take remarkably different forms.
Alabaster is a fine-grained rock gypsum, appreciated by sculptors since prehistory because it is beautiful but soft enough to carve. These and other less chemically pure but more common forms of gypsum are mined or quarried virtually all over the world. Gypsum is bulky stuff, so it is expensive to transport any distance. Manufacturers of wallboard, plaster of Paris, portland cement, and agricultural gypsum for soil conditioning thus usually set up shop near deposits of the mineral. However, gypsum deposits aren't to be found everywhere.