Chalcedony is a fibrous quartz formed at temperatures of below 100 degrees Celsius out of solutions rich in silicic acid. These solutions percolate through fine cracks and veins in rock and collect in larger clefts where they solidify and crystallize. Blue chalcedony obtains its colour through bending light through the microscopically fine crystals (the Tyndall effect), whereby the red portion of the light is absorbed and the blue portion is reflected. 
Sometimes called sapphire in ancient times, blue chalcedony was sacred to the Classical moon and huntress goddess Diana. Among the Amerindians, blue chalcedony was made into arrowhead amulets to bring good fortune and protection. In antiquity, chalcedony was already known to represent the elements of air and water. As such, it was employed for healing illnesses connected with the weather, such as colds and circulatory problems. 
Spiritually blue chalcedony is the stone of telepathic psychic communication. It represents both aspects of the communication: the ability to listen and to understand, as well as the ability to communicate effectively. It encourages the pleasure of contact with other humans, with animals, plants and beings from all worlds. 
Emotionally chalcedony bestows a light-heartedness, a carefree, elated feeling for life with an optimistic tenor. It enhances conscious self-awareness through improving perception of our feelings, emotions, desires and needs. This helps us learn the true motives for our actions and are then able to change them if necessary. Hold chalcedony in the palm of your hand and it will absorb stress and irritability, replacing them with a sense of calm and happiness.
Mentally chalcedony is the reality factor, replacing illusions and vague promises with practical plans and realistic timescales for any joint or collective venture. Blue chalcedony improves oratory, verbal dexterity and the ability to speak foreign languages. For this reason, chalcedony is known as the stone of diplomats.
Physically chalcedony alleviates problems of the respiratory tract such as colds or the effects of smoking. This fabulous stone enables the fluids of the body to flow correctly, thus avoiding a build-up of pressure, for example behind the eyes or in the mucous membranes. It eases hay fever and plant allergies and may speed the dissolving/passing of gall and kidney stones. 
Revitalize chalcedony in running water.