Rock Type: Quartz-muscovite-garnet metasediment
Location: Guyana, South America
Description: The medium-grained
quartz demonstrates undulose extinction(wavy grey to black). The extremely birefringent (bright coloured) muscovite grains form coarse broad crystals. Garnets (black) commonly contain quartz inclusions. This rock was originally a sediment that has been subject to heat and pressure that resulted in the growth of garnet and alignment of micas into bands. The rock was studied for its gold potential.