Blue Chalcedony Tower. $40.00. 1.4 x 1.1 x 3.9 in. A very nurturing stone, chalcedony improves mental flexibility and memory. It also is great for voice dexterity, making the stone useful to have around during public speaking events and while learning new languages. Generosity, optimism, and gentle, yet powerful assertiveness are also aspects of chalcedony.