Summary: Glushinskite, a dihydrate of magnesium oxalate, occurs at the lichen/rock interface on serpentinite colonized by Lecanora atra at Mill of Johnston, near Insch in north-east Scotland. It is found in a creamy white layer intermingled with the hyphae of the lichen fungus. It consists of crystals mainly 2 to 5 µm in size showing a distorted pyramidal form, often with curved and striated faces. X-ray, infrared, and chemical data are given.