Summary:
Distinctive features are 1) a scaly cap with tinges of blue-green, pink, vinaceous-red, and/or other colors, 2) yellowish gills, 3) bitter taste, 4) growth on wood, and 5) rusty orange spores. Gymnopilus aeruginosus is estimated to be moderately active as hallucinogen.

Cap:
(2)5-15(23)cm across, convex to nearly flat; at first dull bluish green "or variegated with green, yellow, salmon, red, or vinaceous", sometimes fading to buff or pinkish buff when old; dry, fibrillose-scaly with small tawny to reddish to dark brown scales (or cracked when old), (Arora), 2-5cm across, more rarely 6-23cm across, convex; 'at first dull bluish gray-green, or aeruginous to variegated green and yellow, at times with patches of salmon or livid red, becoming "warm buff" to "pinkish buff," or at times brown or drab, especially when dried'; dry, fibrillose-scaly, becoming rimose-areolate [cracked like dried mud], "each areola with 2-8 cushion-like to fibrillose scales", or sometimes squamulose [finely scaly] without areolae, "the scales tawny or blackish, margin even", (Hesler), becoming warm pinkish buff then drab brown when dried (Phillips)

Flesh:
pallid or whitish, tinged greenish, or dull bluish green, when dry becoming yellowish to vinaceous', (Hesler), "whitish or tinged blue or green", (Arora), drying yellowish or pinkish brown, (Phillips)

Gills:
"adnexed to adnate or slightly decurrent, often seceding", close; buff to yellow-orange or ocher, (Arora), "adnexed to adnate, often at first decurrent by a line, frequently seceding", crowded or close, broad to medium broad, numerous subgills; "cream buff" to "pale ochraceous orange", edges even to slightly rough, (Hesler)

Stem:
(3)5-12cm x (0.4)1-1.5(4)cm, more or less equal; similar color to cap; dry, smooth or fibrillose, (Arora), (3)5-12cm x (0.4)1-1.5(4)cm, equal, "solid, becoming more or less hollow", at times 3-8 fruiting bodies connate (joined) at base; colored as cap; dry, appressed-fibrillose or bald, sometimes striate, (Hesler), sometimes lined with a hairy base, (Phillips)

Veil:
yellowish, fibrillose, often scanty, leaving an evanescent [fleeting] zone of hairs near top of stem, (Arora), arachnoid [cobwebby], yellowish, slight, fugacious [fleeting], leaving a evanescent zone at top of stem, (Hesler)

Odor:
mild, or can be oily farinaceous odor with slight anise component, (Hesler), mild (Phillips)

Taste:
bitter (Hesler, Arora, Phillips)

Microscopic spores:
spores 6-9 x 3.5-4.5 microns, elliptic, rough, (Arora), spores 6-8.5(9) x (3.5)4-4.5 microns, elliptic in face view, inequilateral in side view, verruculose [finely warty], "no germ pore, ferruginous in KOH, dextrinoid"; basidia 4-spored, 24-29 x 5-7 microns, basidioles sometimes present, 22-27 x 5-6 microns, clavate, brown; pleurocystidia rare, 23-35 x 5-7 microns, ventricose, cheilocystidia 20-38 x (3)5-7(9) microns, "flask-shaped to ventricose, capitate, subcapitate, more rarely non-capitate", sometimes extending up the sides of the gill a short distance; clamp connections present, (Hesler)

Spore deposit:
rusty to rusty orange or rusty cinnamon, (Arora), "orange-rufous", "ferruginous", "xanthine-orange", or "cinnamon rufous", (Hesler), dark reddish orange or brownish rust (Phillips), rusty brown to rusty orange to reddish cinnamon (Stamets)

Notes:
G. aeruginosus has been found at least in BC, WA, OR, and ID. Hesler(2) studied material from WA, ID, CA, MI, NC, PA, and TN. There are collections from BC at Pacific Forestry Centre and the University of British Columbia (some as Pholiota aeruginosa). Stamets(1) adds OR, OH, central to northern Europe, and Japan.

EDIBILITY

no (Phillips), hallucinogenic (Arora, Stamets)

Synonyms and Alternate Names:
Pholiota aeruginosa Peck