An outstanding boulder. The BGS has this to say about the geology of the area:
Tulaichean Schist Formation – Semipelite And Psammite. Metamorphic Bedrock formed approximately 542 to 1000 million years ago in the Period. Originally sedimentary rocks formed in shallow seas. Later altered by low-grade metamorphism.
You can say that again – a wonderful colourful mix of sedimentary wiggle shapes and coarse schist with marbling layers through it.