This garnet-kyanite schist has a long history. It was originally deposited as silts and muds about 800 million years ago between North America and an island in the eastern Atlantic romantically called Avalonia. Following years of sediment accumulation and deepening burial, a gradual closure of the Altantic Ocean forced a collision between Avalonia and North America roughly 400 million years ago. The high temperatures and pressures associated with deep burial plus the strong compressional forces caused the ordinary sediments to recrystallize into the rock you see above. Metamorphic petrologists have to do a great deal of careful mineralogical and geological study to reconstruct such details as the following: the probable starting rock, the timing and duration of deformation, the temperature (burial ± nearby magmas?) and pressure (burial depth) history, and how these details record the geologic history of a region.

The reddish brown 'turds' are garnets. You can just make out some bluish-gray kyanite crystals, the white areas are mostly quartz, and the rest is largely muscovite. This rock image is approximately life-sized.