Cortinarius traganus, also known as Gassy webcap, has a convex to an umbonate, fleshy, silvery violet cap. It is mycorrhizal, usually with deciduous trees, but also found with conifers, often on acidic soil.
initially spherical to convex, with the margin rolled inward, later flattened, sometimes with a large, broad, central umbo. The margin often cracks star-like, particularly in dry weather. Color first pale azure violet to pale lilac colour, later fading to tan-brown or rusty brown. The surface is dry, silkily shiny or tomentose at the margin with membranaceous bronze fragments of the veil, it becomes later cracked into small scales. Gills
sub-crowded, quite thick, broadly adnate, and often slightly emarginate. Colour slightly dirty violet when young, later brown. Stem
tough and thick, bulbously at the base, and spongily stuffed inside. It is vivid violet for a long time in the upper part above the cortina, paler below, and covered with a tough, whitish, boot-like veil, which usually leaves upright zones on the stem. The cortina is violet. The flesh is saffron yellowish-brown to yellowish-brown from the beginning except at the tip of the stem where it is dirty violaceous. It has a strong, bitter taste, particularly when young.
Cortinarius malachius has a slightly scaly cap. Cortinarius camphoratus is similar in appearance and is also violet, but it has pale violet gills which soon turn rusty, and a longer stem with paling flesh at the base. It is associated with conifers, as are Cortinarius alboviolaceus.