Scientifically the term   CHALCEDONY   refers to any type of micro-crystalline Quartz.  However, in the gem and healing trade it describes a blue, white or other lightly colored nodular or massive type.    CHALCEDONY often occurs as a lining to amygdales and geodes in the Karoo basalts, and some of the best specimens coming out of Southern Africa come from the manganese fields in the Kalahari and in the north east of Namibia. 

BLUE CHALCEDONY is used by light workers and healers to aid communication, encourage acceptance of new situations, and enhance self-awareness.   It is believed to reduce respiratory disease and help lower both blood pressure and a high temperature.