The violaceous colour and fibrillose-striate stipe are distinctive far Entoloma nigrovÃ¬olaceum. Entoloma viiduense differs by having distinct blue-coloured fruitbodies when young, and a polished stipe.
Pileus 10-50 mm broad, hemispherical to convex then expanding, slightly depressed to distinctly umbilicate with involute then deflexed margin, not hygrophanous, not translucently striate, dark violaceous-black at first then violaceous-brown, entirely tomentose or squamulose, then radially fibrillose and glabrescent at margin, almost squarrose at centre. Lamellae, L = 24-40, l = 3-7, moderately distant, broadly adnate to deeply emarginate, segmentiform to ventricose, white then pink, finally sordid grey-pink or brown-pink, with concolorous, entire edge. Stipe 25-70 × 3-5(-7) mm., cylindrical or compressed, violaceous or violaceous-grey, at apex concolorous with pileus, downwards slightly paler, minutely pruinose at apex, downwards silky striate, never entirely smooth, sometimes scattered flocculose-squamulose, white tomentose at base. Context pale blue violaceous in cortex and white in inner parts.
Smell not distinctive.
Taste mild or oily-rancid.
Spores (9.0-)9.5-13.5 × 7.0-9.0(-10.0) µm, Q = 1.2-1.7, irregularly 6-9 angled in side-view. Basidia 4-spored, clampless. Lamella edge fertile. Cheilocystidia absent. Pileipellis a transition between a cutis and a trichoderm at margin, towards centre more distinctly a trichoderm or forming a transition to a hymeniderm, made up of inflated terminal elements, 35-120 × 15-30 µm. Pigment violaceous, intracellular in pileipellis. Clamps absent.
Habitat: In mossy grasslands, also found among living Sphagnum. Aug.-Sept.
Distribution: So far only known from a few localities in Scotland.