CAP: (4-12 cm) wide, convex, becoming broadly convex to nearly flat; surface dry and velvety when young, occasionally finely cracked in age, dark brown or gray-brown, yellow-brown or reddish brown when young, becoming dull cinnamon-brown in age, staining vinaceous with NH₄OH or KOH; flesh whitish to pale yellow, blueing quickly when cut; odor and taste not distinctive.

PORE SURFACE: typically dark brown when young, becoming reddish brown or brownish orange in age, quickly staining blue or blue-black when cut or bruised; pores circular, 2-3 per mm.

STALK: (4-9 cm) long, (1-2 cm) thick, equal or enlarging slightly downward, solid, brownish pruinose over a dull yellow ground color, staining blue-black when bruised; partial veil and ring absent.

SPORE PRINT: olive-brown.

MICROSCOPIC FEATURES: spores 11-15 x 4-6 μm, suboblong to nearly fusiform, smooth, pale brown.

FRUITING: scattered or in groups on the ground, usually under hardwoods; July-September; infrequent.

EDIBILITY: unknown.

COMMENTS: Boletus vermiculosoides (edibility unknown) is very similar but has a yellow cap when young that becomes brown at maturity and stains dark brown with KOH, a whitish to yellow or olive-tinged stalk, yellow flesh that bruises blue and stains yellow with KOH, and smaller spores, 9-12 x 3-4 fim.

From Mushrooms of Northeastern North America Alan E. Bessette, Arleen R. Bessette, & David W. Fischer  Copright © 1997 Syracuse University, ISBN 0-8156-0388-6