Gypsum, the Mineral About the House

     Gypsum is a very soft mineral. It only measures a 2 on the Mohs scale of hardness so you could easily scratch it with your fingernail! Gypsum is an evaporate mineral, it is usually white, yellowish white, or colorless; and its transparency ranges from transparent to opaque. Transparent crystals of gypsum are called selenite. Gypsum crystals belong to the monoclinic crystal group and look like flat parallelogram-shaped prisms. Gypsum can also have needle-like crystals and fibrous crystals. Fibrous gypsum crystals are sometimes called satin spar. Gypsum’s needle-like crystals are sometimes found growing in a radiating pattern. They kind of look like flowers and are called “daisy gypsum.” Gypsum crystals often twin to form arrowhead-shaped twins called “fishtails” or swallowtails.” Gypsum sometimes forms what is called a “desert rose,” which you can see at the bottom of the picture.
     When gypsum is heated it looses a lot of the water that makes up part of its chemical structure. If you add more water to this dehydrated mass it will become gypsum once again and will harden into a solid piece. This is how plaster of Paris is made. Gypsum is also used to make a type of wall board (sometimes called “gypsum board”) that is used in drywall construction. If you live in a house that is made with these kinds of walls then you are surrounded by a lot of gypsum!
     Gypsum is found in many places throughout the world. Some hard water deposits are gypsum so every time you have to scrub that white stuff off of your shower head it’s possible that you might be scrubbing away gypsum! A lot of gypsum (enough to be mined) can be found in these places: Great Britain, Canada, Italy, and these U.S. states: Michigan, New York, Ohio, Iowa, and Texas. France is another source of gypsum. Plaster of Paris was actually named for the Paris basin where gypsum can be found.
     Gypsum is a fairly useful mineral, it’s quite soft, and its crystals can make some pretty interesting formations. All of these facts are cool, but I think that the most captivating one is that I am surrounded by gypsum every day!