Spore print colour: what purple-brown, black, white and pale grey tell you
Before anyone had a microscope, mycologists sorted mushrooms by the colour of the dust they left behind. The spore print is still the fastest taxonomic test there is, and reading one well tells you the genus, the pigment state and sometimes the strain family in a glance.
01Colour by genus
- Purple-brown to near black: Psilocybe. Cubensis prints are the reference: dense, deep purple-brown, sometimes with a violet cast at the edge of the deposit.
- Jet black: Panaeolus. Pan Cyan prints are black with no brown in them, which is the quickest way to separate the two genera.
- Lighter brown: Ochra lines (Psilocybe ochraceocentrata) tend to print browner and less dense than cubensis, though the difference is one of degree.
- White, cream or lilac: gourmet and wild species such as oyster and lion's mane. A white print on white paper is invisible, which is why prints are taken on foil or half black, half white card.
- Rusty brown: many wild genera. If a supposed cubensis prints rust, it is not cubensis.
02Colour by pigment state
Within a species the print also reads pigment. An albino cubensis line (APE, Jack Frost, ABV) leaves a pale grey to off-white deposit because its spores carry almost no pigment. A leucistic line, pale in the cap but with pigmented spores, prints a normal purple-brown. This is the single cleanest way to tell "true albino" from "leucistic" without a microscope, and it is the test the library uses when a card says one or the other.
Before anyone had a microscope, mycologists sorted mushrooms by the colour of the dust they left behind.
03Density and pattern
A dense, even, gill-patterned print says a heavy-sporing line and a well-taken deposit. A faint, patchy one says either a low-spore family (Penis Envy and its descendants), a small-capped species (Panaeolus), or a print taken from a cap past its best. The radial gill pattern itself is a check that the print is genuine and undisturbed.
04Taking a print for study
A print is the deposit a cap leaves on foil or paper. For microscopy the library supplies prints already taken and sealed; a few spores are lifted with a sterile blade into a drop of water on the slide. Prints are the archival format: sealed and dry, out of light, they keep for years and record colour in mass in a way a syringe cannot. The format comparison covers when to choose one.
05Recording colour honestly
Colour is subjective and light-dependent. Record it against a fixed reference (the same white card, daylight from a window) and photograph the print with a colour reference in the frame. Then compare prints to each other rather than to memory. Cubensis next to Pan Cyan next to Jack Frost on one sheet is a lesson in three deposits.
Specimens for this story: ACS Ochra, MFH Ape, DreadMaw (Gamma Decay iso) and Whitebilly, all prepared under sterile protocol and LOT-logged in the UK.
Questions people ask
What colour is a Psilocybe cubensis spore print?
Deep purple-brown, dense and even, sometimes with a violet cast. Albino lines print pale grey.
How do I tell an albino strain from a leucistic one?
Print it. A true albino leaves a pale grey deposit; a leucistic line leaves a normal purple-brown one because its spores are still pigmented.
Why is a Pan Cyan print black and a cubensis print purple?
Different genera carry different spore pigments. Black in mass is a defining character of Panaeolus; purple-brown of Psilocybe.