Growing singly or subfasciculate on decaying coniferous wood (e.g. Picea, Pinus), more rarely on hardwood. Summer to autumn. Widespread in the covered area, generally rather rare, but locally common, absent or rare in the northernmost parts of Scandinavia. It seems to be a rather common species in southern Norway, rare in northern parts, but recorded north to Finnmark.

Pileus 5-40 mm across, conical to campanulate, becoming almost plane with umbo, sulcate, translucent-striate, glabrous, somewhat lubricous when wet, at first dark brown with almost blackish violet centre and pale brown margin, with a violet shade, becoming grey brown or grey to dark grey with a somewhat darker centre, and a faint violet shade. Lamellae 20-30 reaching the stipe, ascending, narrowly adnate, sometimes decurrent with a short tooth, dorsally intervenose with age, white to grey with a very distinct violet edge. Stipe 25-70(-100) x 1-3(-5) mm, hollow, terete, equal or somewhat widened below, straight to curved, pruinose, glabrescent, smooth, but with age somewhat grooved lengthwise, grey-brown to greyish violet, towards the base usually darker brown with a violet shade, the base covered with white fibrils, often rooting. Odour and taste none (also experienced as +/- raphanoid).

Basidia 27-36 x 10-12 μm, clavate, 2- or 4-spored. Spores (7.5-)9-12.2 x (5.5-)6.2-8.2(-9) μm, Q 1.2-1.5, Qav≈ 1.3, broadly pip-shaped, smooth, amyloid. Cheilocystidia 17-61 x 9-29 μm, forming a sterile band, clavate, fusiform, utriform to subcylindrical, smooth and apically usually broadly rounded, with lilaceous contents. Pleurocystidia absent. Lamellar trama dextrinoid, faintly reddish brown or vinaceous brownish in Melzer's reagent. Hyphae of the pileipellis 1.5-6 μm wide, gelatinized, smooth to sparsely covered with warts or fairly coarse, cylindrical excrescences 2.5-11 x 1.5-3.5 μm. Hyphae of the cortical layer of the stipe 2-3.5 μm wide, smooth or sparsely diverticulate, terminal cells narrowly clavate, to much wider and strongly curved, smooth or coarsely diverticulate. Clamp connections generally absent or very rare.

Microphoto of cheilocystidia

Mycena purpureofusca is a member of sect Rubromarginatae. Maas Geesteranus (1986c) discussed how to separate it from M. rubromarginata and mentioned the cheilocystidia as a reliable character. The cheilocystidia of M. purpureofusca have broadly rounded apices, whereas those of M. rubromarginata have narrow necks. He also mentioned the clamp connections as a character to separate the two species. M. rubromarginata always have clamps, while in M. purpureofusca they are absent or very rare. Mycena sanguinolenta has less violet shades, very pointed cystidia and a red sap that can be overlooked. See also Kasparek (1995).