Fig. 4a. Swapped replacing K-feldspar crystals (K₁' , K₂', occurring at the grain boundary between the two differently oriented preexisting (probably primary) K-feldspar crystals (K₁, K₂). Huangnitian quartz syenite. Q = quartz; Hb = hornblende. Under plane-polarized light. Scale bar = 0.5 mm.