The massive, generally fine-grained form of Gypsum is known as Alabaster. And, due to impurities, may be almost any color from white to near-black. It is a soft mineral, and can be readily carved with hand-tools. In the area around Cap Rock Canyon in the Texas panhandle, one can see periodic outcroppings of alabaster. From the road, it stands-out as white against the red sand/dirt. In addition to the water in its molecular structure, Alabaster will absorb water from the surrounding soil. So, should you find alabaster in the field, it is recommended to allow the rock to dry in an controlled environment. Otherwise, it can develop cracks. Also, one can tell if the Alabaster has been exposed very long by closely examining the surface. Frequently, one will find tiny traces of water erosion. Common wisdom holds that 'fresh' Gypsum is better for carving than 'sugary' (once you see alabaster with water erosion, this term will make sense).
Satin Spar is another form of Gypsum found in the panhandle of Texas. This Gypsum is fibrous, and forms in more-or-less horizontal seams, with the fibers running vertically. Colorless Satin Spar, makes fascinating spheres. When looking through the ends of the fibers, one can seen an image of an object on the other side of the sphere. When looking 'across' the fibers, spheres can show a stunning "cat's eye" effect. Thinner pieces of Satin Spar, when saturated with water, can become quite flexible (and fragile). Then, when dry, return to their familiar rigid rock-like character.
Crystallized Gypsum is generally called Selenite. Some of the largest individual crystals in the world are Gypsum crystals located in Mexico. Gypsum can crystallize very quickly, as seen in the Great Salt Plains National Wildlife Refuge. This location is famous for "hour glass" crystals that have sand or mud inclusions that frequently resemble an hourglass. And, crystals grow so quickly that managers are able to rotate the collecting area to a different grid area every year or so to assure availability of fresh crystals. We are unable to offer any of these crystals for sale, as collection is limited to personal use.
Selenite may also crystallize in clusters that can resemble flowers. The shape is the result of inter-growth of thin bladed crystals. These occur in multiple locations around the world, and are known variously as Desert Rose, Gypsum Rose, Selenite Rose, etc. Colors vary, depending upon whether inclusions (frequently sand) are present. We have several varieties of Gypsum at Crystal Moon Gallery, and enjoy talking about this fascinating mineral.
