Psilocybe semilanceata, commonly known as the liberty cap, is a psychedelic

Psychedelic mushroom

Psilocybin mushrooms are fungi that contain the psychoactive compounds psilocybin and psilocin. There are multiple colloquial terms for psilocybin mushrooms, the most common being shrooms or magic mushrooms....

 (or "magic") mushroom that contains the psychoactive compounds psilocybin

Psilocybin

Psilocybin is a naturally occurring psychedelic prodrug, with mind-altering effects similar to those of LSD and mescaline, after it is converted to psilocin. The effects can include altered thinking processes, perceptual distortions, an altered sense of time, and spiritual experiences, as well as...

 and baeocystin

Baeocystin

Baeocystin is a mushroom alkaloid and analog of the psychedelic hallucinogenic drug psilocybin, a tryptamine derivative. It is found as a minor compound in most psychoactive mushrooms together with psilocybin, norbaeocystin, and psilocin...

. Of the world's psychoactive mushrooms, it is the most common in nature, and one of the most potent

Potency (pharmacology)

In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...

. The mushrooms have a distinctive conical to bell-shaped cap

Pileus (mycology)

The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...

, up to 2.5 cm (0.984251968503937 in) in diameter, with a small nipple-like protrusion on the top.