Selenite

Hardness: 2-2.5 on the Mohs scale (very soft, can be scratched with a fingernail). Color: Typically white, colorless, or yellowish, often with an opalescent or silky sheen due to fibrous inclusions. Luster: Pearly to silky. Crystal Structure: Monoclinic, often forms in fibrous masses, sometimes as large, well-formed crystals. Cleavage: Perfect in one direction, creating thin sheets or fibers. Specific Gravity: 2.3-2.32.

Selenite is a variety of the mineral gypsum (hydrous calcium sulfate). It forms primarily through the evaporation of saline water, such as in ancient seas, lagoons, or salt lakes. As water evaporates, the concentration of dissolved minerals increases, leading to the precipitation and crystallization of gypsum. It can also form from hydrothermal solutions. Its geological age varies greatly depending on the depositional environment, ranging from relatively recent to millions of years old.

Industry: As a source of calcium sulfate, gypsum (including selenite) is widely used in plaster, drywall (plasterboard), cement, and agricultural soil amendments. Jewelry/Decorative: While too soft for conventional jewelry, selenite is often carved into decorative items, lamps, wands, and spheres due to its attractive luster and ability to transmit light. It is commonly used in metaphysical practices for cleansing and energy work due to its purported calming properties.

Selenite is named after Selene, the Greek goddess of the Moon, due to its soft, pearly luster resembling moonlight. It is one of the most common evaporite minerals. Unique among gypsum varieties, selenite can form exceptionally large, transparent crystals, such as those found in the Naica Mine in Mexico, where some crystals are over 10 meters long.

Field Identification: Selenite is easily identified by its extreme softness (can be scratched with a fingernail), pearly to silky luster, and perfect cleavage which allows it to be split into thin, flexible sheets. It often has a fibrous appearance or chatoyancy (cat's eye effect) when polished into beads like those in the image. Common Locations: Significant deposits are found worldwide in sedimentary basins, including vast beds in the United States (Oklahoma, Utah, Arizona, New Mexico), Canada, Mexico, Spain, Italy, Australia, and many other countries. Collector Tips: Handle selenite with care due to its softness. It can be scratched easily and will dissolve over time in water. Specimens with high clarity, large size, or interesting crystal forms are highly valued.