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Microstructure characteristics of agate samples BH01 and BH02 observed under CPL. (a) Agate BH01 with two different structural sequences. (b) Enlarged view of the type I sequence in region BH01-1. (c) Enlarge view of the type II sequence in region BH01-2. (d) Agate BH02 shows the type II sequence. (e, f) Enlarged view of region BH02-1 in Figure 2d. The red arrow indicates the growth direction of banded agates. Pg, pseudo-granular silica. Ch, chalcedony. Qtz, quartz.
