Superb, sharp crystals to 1 cm, translucent, look like purple corundum. Instead they are this rare iron sulfate. This strange mineral is rarely found in specimens larger than a thumbnail or a crust with small crystals. Here is a small cab, with rich purple color (the lighting makes it look more even than in person, where I admit the color is more splotchy in appearance). Still, it is not unattractive and this is the best Utah specimen of the mineral I have seen for sale. Not stable in high humidity, I am told (this piece has clearly lasted many decades already, so it is not highly unstable, either). Marty's number on this was 1718, indicating an early acquisition date.