Rock Type: Quartz-muscovite pegmatite
Location: Guyana, South America
Description: The large coarse quartz demonstrate undulose (wavy grey-black) extinction after experiencing stress (pressure or stretching). The muscovite crystals (bright colours) form coarse broad crystals and occasionally include tiny crystals of quartz and zircon. The muscovite grains show minor retrogression or breakdown to chlorite, and very small Ti-magnetite (black) has grown along cleavage planes (internal lines). The rock was studied for its gold potential.