Selenite is a crystalline variety of the mineral gypsum, a hydrous calcium sulfate, known for its luminous, often translucent appearance. Its name is derived from the Greek word for the moon, referencing its soft, pearly glow. Because of its popularity, distinguishing a genuine specimen from a common imitation can be challenging. This guide provides practical methods and mineralogical details to help verify the authenticity of selenite.
Visual Characteristics of Genuine Selenite
Genuine selenite exhibits distinct visual features stemming from its crystal structure. The true mineral form is typically transparent and colorless, sometimes called “true selenite,” forming in large, clear, flat plates. The variety commonly used in wands and towers is satin spar, which is also gypsum but has a fibrous structure that makes it translucent and milky white.
The fibrous nature of satin spar creates a silky, shimmering optical effect known as chatoyancy, or the “cat’s eye” effect, as light reflects off the parallel fibers. Both varieties display perfect cleavage in one direction, allowing them to easily split into thin, flexible sheets. Look closely for parallel striations or growth lines running along the length of the crystal, which indicates its natural formation.
Hands-On Identification Tests
The most definitive way to test a specimen is by assessing its resistance to scratching. Selenite is exceptionally soft, ranking at a 2 on the Mohs scale of hardness. A genuine piece can be easily scratched, or even indented, with a clean fingernail, which has a hardness of approximately 2.5.
If a fingernail fails to leave a mark, the material is likely not selenite. A copper penny, which has a hardness of about 3.5, would scratch a genuine selenite sample with minimal effort. The mineral’s low density also means a large piece of selenite will feel relatively lightweight compared to denser minerals like quartz or glass.
Another simple test involves thermal sensation, since minerals and artificial materials conduct heat differently. Selenite acts as a moderate thermal insulator, meaning a genuine piece should feel cool to the touch but warm up slowly in your hand. In contrast, common imitations made of plastic or resin will feel warmer almost immediately and may lack the solid, dense feel of a crystal.
Common Imitations and Key Differences
Many materials are substituted for selenite, but they fail the simple hands-on tests due to differences in physical properties. Glass is a frequent substitute, but it is substantially harder, ranking around 5.5 on the Mohs scale. Because of this hardness, glass cannot be scratched by a fingernail or a copper penny, and it lacks the natural internal striations and perfect cleavage planes seen in selenite.
Plastic or resin imitations are also common, especially for carved items like spheres or wands. These fakes will feel warm and may display tell-tale signs like small air bubbles trapped within the material, characteristic of a manufactured product. The soft, satiny luster of genuine selenite also differs from the highly uniform, sometimes overly glossy shine of a fake.
If a specimen passes the scratch test and displays the fibrous sheen or characteristic transparency, it is highly likely to be a true variety of gypsum. The combination of extreme softness, perfect cleavage, and unique optical effects provides clear verification against harder minerals or manufactured synthetic materials.