Gypsum is a common sedimentary rock. It is very soft, one of the predominant traits of this rock family. Due to its softness, it has little value as a building material. However, humans use this stone for everything from fertilizer to plastics because of its other useful properties.
Sedimentary Rocks
Sedimentary rocks are a classification of rocks that form from gems or minerals mixed with soil. Typically, this mixture washes down a river and becomes deposited on the bed of a large sea or lake. Over time, as the layers of sediment build up, the older deposits receive a large amount of pressure. This hardens the particles into sedimentary rocks. Because this geologic force is not as extreme as the other processes used to make igneous or metamorphic rocks, sedimentary rocks are "soft" rocks that break apart easily.
Evaporite Mineral
Gypsum is an evaporate mineral too. This term means that it forms in evaporate beds. These are beds that once were at the bottom of the sea. Through different geological methods, such as the moving of land masses or the lowering of sea levels, these beds became exposed to the open air. The Earth's atmosphere then evaporates the remaining moisture from the bed.
Softness
One of the major characteristics of gypsum is its softness. On the Moh's hardness scale, gypsum only earns a 2 rating. In fact the word "gypsum" comes from the Greek word for "chalk." When it becomes dehydrated, its softness allows the mineral to easily crumble into a chalk-like substance. For this reason, gypsum often was used for sculptures as long ago as Ancient Egypt. In modern times, gypsum forms the basis of sculpting materials, like Plaster of Paris.
Crystalline Content
Gypsum mainly occurs as a crystal in nature. These crystals grow either in long fibers or large masses. Some of the fibers grow to great lengths, especially in arid conditions, creating crystalline shapes up to 39 feet long. Most gypsum is transparent, but a prized variety has a slightly white shade. This is alabaster, a stone used for artistic purposes. Alabaster occurs in many types of artwork from small ornamental boxes to great sculptures.
Sulfur Content
Gypsum primarily is made up of sulfur. This is due to the evaporative process that creates the mineral. By the start of the 19th century, farmers realized that adding sulfur to the soil helped plants to grow. Therefore, many used crumbled gypsum as a natural fertilizer. In fact, American farmers became so desperate to get this fertilizer that it led to a smuggling trade with Nova Scotia, which caused the War of 1812.
Modern fertilizers still use gypsum, and it is still an ingredient for many types of plaster. There are multiple gypsum mines all over the world due to the demand of this mineral by modern industry. While gypsum has a practical purpose, it is also quite lovely in its natural form. Many rock collectors preserve gypsum crystals simply for the beauty of the stone.
Gypsum becomes Plaster of Paris when it is heated under the correct conditions.
Plaster of Paris can be spread when wet, and then hardens to a rock-like consistency. Wallboard or ‘gyproc’ is essentially a gypsum sandwich: pieces of heavy cardboard enclosing a thin plaster sheet.
Limestone and gypsum both contain the element calcium. Gypsum is a calcium
sulphate combined with some water, and limestone is a calcium carbonate.
New Brunswick’s gypsum deposits are found within sedimentary rocks of the Mississippian age. They were deposited about 325 million years ago, crystallizing from large, slowly evaporating bodies of seawater. More than two dozen gypsum quarries have been worked around Hillsborough in southeast New Brunswick. As a result of all the mining in the area, sinkholes have developed over time so please use caution.
Or – the Chemist’s version 
Gypsum is a non-metallic mineral, found in rock form. It is composed of 79.1% calcium sulphate and 20.9% water, by weight. Chemists call it Hydrous Calcium Sulphate, and as there is one molecule of calcium sulphate combined with two molecules of water. It has the chemical formula CaSO42H20. By volume this works out to nearly 50% water in the mineral structure. This water however, is perfectly dry, and is known as "water of crystalization". It could be compared with ice, which, too is water in crystaline form, but there is this an important difference; ice will melt, or change to water, when it is exposed to a to temperature above 32 F. Water of crystalization, in gypsum, does not change until it is subjected to heat above 212 F but at that temperature the water of crystalization changes form and becomes water vapor and is driven off from the gypsum just as steam is driven off from water at 212 F.
The coordinates take to one of many sinkholes in the area. To claim this cache, please estimate the size of the gypsum "sinkhole" at the posted coordinates as well as the height of the wall behind it. Feel free to post a picture of yourself at the coordinates, holding your GPSr and a piece of the gypsum mineral but that is not a logging requirement.
http://www.gnb.ca/0078/minerals/pdf/limestone_gypsum-e.pdf
http://www.museevirtuel-virtualmuseum.ca/sgc-cms/histoires_de_chez_nous-community_memories/pm_v2.php?id=story_line&lg=English&fl=0&ex=00000550&sl=4355&pos=1&pf=1
http://geology.answers.com/gems-and-minerals/characteristics-of-gypsum-rock