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Triassic Sherwood Sandstone Group, County Antrim, Northern Ireland, U.K., a polycrystalline quartz grain of metamorphic origin. The grain has sutured internal boundaries between composite crystals and a preferential alignment of the constituent crystals. In addition, crystal boundaries are diffuse. XPL, AFeS, KFS, BDI, Scale bar = 0.07 mm. From From AAPG Memoir 109—A Color Guide to the Petrography of Sandstones, Siltstones, Shales, and Associated Rocks, [http://store.aapg.org/detail.aspx?id=1250 Chapter 1].