Aphthitalite is a mineral primarily composed of potassium sulfate with some admixture of sodium sulfate. Synonyms for aphthitalite include pyracmonite, sal polychrestum, mirrorstone, and feuerstein. These terms refer to the same mineral and can be used interchangeably in academic literature and other contexts. However, the different names can reflect various regional uses or historical contexts. For example, "mirrorstone" might refer to the use of the mineral for mirrors in ancient times, whereas "feuerstein" is the German word for "firestone," reflecting its use in the manufacture of gunpowder. Regardless of terminology, aphthitalite is an important mineral in chemical and geological research and has many applications in industry and technology.