The cap of Calonarius olympianus is starts out light purple in color, before becoming whitish or sometimes yellowish as the mushroom getsolder. It starts out round or convex and becomes flat when the mushroom matures. It is about 3-7 centimeters in diameter. The gills are adnexed to notched. The stipe is about 4-7 centimeters long, 1.1-2 centimeters wide, and purplish in color. A cortina is present, and the spore print is rusty brown. The cap turns pink when potassium hydroxide is applied.