Cap 4.0-8.0 cm broad, convex, broadly so in age; margin incurved, then decurved, frequently wavy; surface whitish to cream, dry, sparsely covered with appressed, brownish fibrils, bruising brownish and sometimes yellowish; context up to 2.0 cm, firm, white to buff, unchanging or slowly to tan-brown; odor and taste mild.
Gills adnexed, close, thin, broad, pallid when young, dark rusty-brown in age from maturing spores; lamellulae in three to four series.
Stipe 3.0-6.0 cm long, 1.5-3.0 cm thick, solid, equal to bulbous at the base; surface matted-tomentose, colored and bruising like the cap, the lower portion frequently dirt encrusted; partial veil fibrillose-membranous, white, persistent, remaining attached to the cap margin at maturity; in age spores released via radial tears in the partial veil.
Spores 10.0-13.5 x 5.5-7.0 µm, finely warted, elliptical to almond-shaped in face-view, inequilateral in profile, i.e. flattened on one side with an opposing belly, hilar appendage inconspicuous; spores dull rusty-brown in deposit.
Solitary to clustered, buried in duff of montane conifers; common in the spring, occasional in the
This montane species recognized by a whitish cap, partial veil which remains attached to the cap at maturity, and tendency to fruit below ground. It is a common find of spring bolete hunters that unintentionally unearth it while seeking their more desirable quarry. Cortinarius verrucisporus is a less common relative that sometimes occurs with C. magnivelatus. It is distinguished by a yellow to tawny cap (at maturity) and yellowish partial veil. Smith and Thiers (1969) described several additional Cortinarii, all of which share the characteristics of a persistent veil and subsurface fruiting. These include Cortinarius wiebae with a whitish to tan-colored cap and fragile gills that are brownish even in youth; Cortinarius bigelowii, very short statured, with a tan cap and marginate, bulbous stipe; and Cortinarius velatus with a vinaceous to purple cap. None of these are common.