Gypsum is the most common of the naturally occuring sulfate minerals. It is found in very extensive, bedded sedimentary deposits all over the world. Millions of years ago the world we know today was covered with water. As creatures like clams, oysters, scallops and other shellfish died, their remains settled to the ocean floor in layers many hundreds of feet thick. As time went on, rock (sedimentary rock) was formed. Some of this resulted in gypsum.
Gypsum is used for a lot of things. It has been used since the earliest recorded history. Chinese, Assyrians and Greeks used gypsum for artistic work in carvings and decorations. It was also used as an inferior plaster and mortar by ancient Egyptians. Later in time, gypsum plaster became known as plaster of Paris because of the long-famous gypsum deposits in Montmarte, a section of Paris.
One major use today is in making gypsum board or sheet rock which is used to make walls in houses and buildings everywhere!