Azurite

Azurite is a soft, deep-blue copper carbonate hydroxide, Cu3(CO3)2(OH)2, also called azure spar and, in the early nineteenth century, chessylite. Wikipedia says Pliny mentioned it under the Greek name kuanos, that it served as a blue pigment in antiquity, and that it is used occasionally as beads and jewellery. Cunningham calls it a receptive stone of water and Venus and says it is used to increase psychic powers, bring prophetic dreams, aid divination and in healing magic. Hall calls it deep blue and associates it with psychic and intuitive development, meditation, channelling, communication and memory. Hall also gives a caution about palpitations. These magical uses are the authors' claims, not tested properties.