SELENITE AND SATIN SPAR ARE NOT THE SAME THING
Yes, they are in the same family (gypsum) and yes they do look similar but here are the main differences:
•Satin Spar is usually cheaper than Selenite.
•Satin Spar is Milky White/Opaque/Shiny and may have vertical lines running down the length of the stone.
•Selenite isn't as easily found as Satin Spar.
•Selenite is transparent and has cleavage.
Sadly, Satin Spar is very commonly mislabeled as Selenite and both are able to be cleaned in water. They do not dissolve. However, they will become more fragile over time. Contrary to urban myth, selenite is only slightly soluble in water. Did you know that what is usually labelled as Selenite may actually be a crystal called Satin Spar? These two beautiful crystals are probably the two most mixed up crystals in the entire metaphysical world! They are the same mineral, a form of of gypsum, but they crystallised differently to form either Selenite or Satin Spar.
Selenite is the most famous of the two names, but Selenite crystals are actually much rarer than Satin Spar. Selenite forms in large flat, transparent crystals that are often called “plates” or “windows”. They have very thin sheets and can flake apart. Utah is famous for it's high quality Selenite plates. Satin Spar is the lesser known of the two names, but it is the crystal that most people are familiar with, and most of the online world calls Selenite. In fact, because the name Selenite is so popular, many retailers continue to call their Satin Spar by the name of Selenite because it's what their customers are expecting to find, so this furthers the confusion. Satin Spar crystals are fibrous and white, often seen in little mountains, as raw rulers or wands, or polished into palmstones and spheres with a “cats eye” effect. Satin Spar has fibre optic properties, which means light can pass through the crystal in a certain direction. If you take a section of Satin Spar, and polished the ends flat, then you will be able to see through it.
Care: Place this piece in the moonlight rays around the time of the full moon. Alternatively place in the sunlight for short periods of time. Selenite is made up of 70% water and its delicate fine form can easily be scratched with a fingernail.