Macroscopic feat.:

• Cap/Pileus: 3-7,5 cm broad, convex, soon expanding to broadly convex, obtusely umbonate. Color bluish, fading to azure, then yellow to yellowish green, often with the margin remaining tinged bluish green. Viscid when wet from a separable gelatinous pellicle. Fragments of the partial veil sometimes present along cap margin. Cap flesh thin, bluish at first, fading to straw color.
• Gills/Lamellae: Attachment adnate to subdecurrent, close, fawn brown to chocolate brown to dark brown with spore maturity, with paler edges.
• Stem/Stipe: 40-110 mm long by 3-12 mm thick, equal to slightly enlarged near the base, bluish green to azure, becoming pale buff. Pruinose above the annulus and covered with fibrillose-floccose scalelike patches below. Partial veil membranous, leaving a fragile, membranous annulus sometimes degrading into an annular zone.

Microscopic feat.:

• Basidio/Spores: Light to purplish brown in deposit, ellipsoid, 7-9 (10) by 4.5-5.5 µm.
• Basidia: 4-spored.
• Cheilocystidia: And pleurocystidia 28-55 by 10-16 µm, 2-4 at the apex, clavate-mucronate to fusiform or slightly lageniform with acute apices.

Habitat: A litter mushroom, thriving in garden-like habitats or soils enriched with manure. Widely distributed, reported from the British Isles, Europe, and northwestern North America.

Comment: Possibly mildly active. No chemical analyses are known to this author. This species differs from its close relative, Psilocybe aeruginosa, in its rapidly discoloring cap, the paler gills, and the lack of veil-formed scales on the cap surface, and its generally smaller stature. In Europe Psilocybe caerulea is more common than Psilocybe aeruginosa (= Stropharia aeruginosa). See also Psilocybe pseudocyanea (= Stropharia pseudocyanea).

source - Paul Stamets "Psilocybin Mushrooms of the World"

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