A piece of Selenite which has a hole in the top to fit a tealight candle.
When lit, it makes the whole crystal glow beautifully.
Satin Spar is a form of Gypsum, which is composed of calcium sulfate dihydrate (meaning it has two molecules of water). It is often called Selenite, which contains no significant selenium; the similarity of names comes from both substances being named from the Ancient Greek word for the Moon. All varieties of gypsum are very soft minerals with a hardness of only 2 on Mohs Scale.