Cap: 4-13 cm; convex, becoming broadly convex; dry; dull; soft; finely, innately fibrillose; olive brown to medium brown or grayish brown, fading to tan; often with a yellow marginal zone, or nearly yellow overall when young—but the yellow quickly becoming brown (in some of my collections the yellow has disappeared completely only a few hours after collecting); when fresh bruising blue to black.
Pore Surface: Dark red-brown to maroon when young, but quickly fading to dull brownish orange; bruising promptly dark blue or black; pores round, 2-3 per mm; tubes dull yellowish, to about 2 cm deep.
Stem: 7-10 cm long; up to about 2 cm thick; slender; more or less equal; covered with tiny tufts of fibers that become brownish when handled; brownish overall, with a yellowish apex and, sometimes, a pale reddish zone; not reticulate; basal mycelium whitish.
Flesh: Whitish or yellowish in cap; yellowish in upper stem; staining sky blue in cap and red in stem when sliced; often becoming riddled with worms and decaying quickly.
Odor and Taste: Not distinctive.
Chemical Reactions: Ammonia reddish on cap surface; orangish on flesh. KOH dark red on cap surface; orange on flesh. Iron salts negative to greenish on cap surface; negative on flesh.
Spore Print: Olive brown.
Microscopic Features: Spores 9-12 × 3-4.5 µ; smooth; subfusiform; yellowish in KOH. Hymenial cystidia mostly fusoid-ventricose; yellow in KOH; to about 50 × 10 µ; inconspicuous. Pileipellis a densely tangled layer of repent to erect hyphae 2.5-8 µ wide; terminal elements cylindric with rounded apices. Caulocystidia utriform to fusoid-ventricose; to about 40 µ long; hyaline to golden in KOH.