Gypsum

Hardness: 2 on the Mohs scale, making it very soft and easily scratched with a fingernail. Color: Typically white, colorless, or grey, but can also be yellowish, brownish, or pinkish due to impurities. Luster: Vitreous (glassy) to pearly, silky in fibrous varieties. Crystal structure: Monoclinic; forms in tabular, prismatic, or acicular crystals. Cleavage: Perfect in one direction, producing flexible sheets, and good in two others. Specific Gravity: 2.3-2.37.

Formed as an evaporite mineral from saline waters (e.g., ancient seas, lakes). It precipitates out of solution as water evaporates, leading to the deposition of large beds. Can also form from volcanic activity (fumaroles) or as hydration products of other sulfate minerals. Geological Age: Found in sedimentary sequences from various geological periods, often associated with halite and anhydrite deposits.

Industry: Primarily used in the production of plaster of Paris (for casts, molds, sculptures), drywall (plasterboard) for construction, and as a fertilizer. It's also used as a fluxing agent in steel production and as a filler in paints and paper. Jewelry/Ornamental: Selenite (a transparent, crystalline variety of gypsum) is sometimes carved or sold as ornamental pieces and often considered a healing crystal. Alabaster (a fine-grained massive form of gypsum) is extensively used for carving sculptures and decorative objects since ancient times.

Gypsum is one of the most common sulfate minerals. The name 'gypsum' comes from the Greek word 'gypsos,' meaning plaster. Desert roses are a distinctive form of gypsum (or baryte) that cluster to resemble a rose, formed in arid sandy conditions. Satin Spar is a fibrous variety of gypsum with a silky luster. Selenite is a transparent, colorless, crystalline variety named after Selene, the Greek goddess of the moon, due to its moon-like glow.

How to identify it in the field: Its exceptional softness (scratchable with a fingernail), often clear to white color, and perfect cleavage allowing it to be peeled into thin, flexible sheets are key identifiers. Fibrous varieties will show a silky luster. Common locations: Found worldwide in thick beds within sedimentary rock formations, especially in arid and semi-arid regions. Significant deposits are found in North America (e.g., White Sands National Park, New Mexico, known for its vast gypsum dunes), Europe (e.g., France, Spain), and the Middle East. Tips for collectors: Gypsum is fragile due to its softness; handle with care. Selenite crystals, particularly large ones, are highly prized for their clarity and form. Alabaster is easily carved, making it popular for artistic endeavors.