To reveal growth process of chalcedony, we observed the textural change from facet quartz crystal to chalcedony by using TEM and OPM. Observed sample is fire chalcedony from Aguascalientres, Mexico. Under OPM, fine growth bands developed at the transition parts from the facet crystal to chalcedony. Straight growth bands, which are parallel to r or m surfaces, change to zig-zag lines within chalcedony. TEM observations show that many Brazil-twin lamellae, dislocations and nano-sized growth bands develop at the transition parts. And also, rounded contrast with 10-100nm size were observed commonly. The rounded contrasts are enhanced by nano-sized inclusions. The nano-sized inclusions cause the defects and decreasing of crystal size.
