It is part of the "fine stones". Blue agate owes its color to the presence of mineral impurities.
Beautiful large "slice" of polished geode, 5 mm thick, with superb transparency, and a wide range of blue and turquoise shades....
Excellent condition.
Length x width = 16 x 14.2 cm; Weight 256 grams
Very careful shipping in addition, (via colissimo in metropolitan France = €8.50; via mondial relay = €5.50), other destinations: to be defined according to distance.