Quartz, Clear (derived from Middle High German “twarc”, meaning “hard” ) is a silica mineral (SiO2), and is associated with the Crown Chakra. It has long been considered to be a sacred stone by peoples of many cultures over the centuries. Pliny the Elder thought it was frozen ice of many years duration. Quartz was used in sacred places such as passage tomb cemeteries, as the mystical substance maban (the material from which Australian Aborigines shamans receive their power), and means “stone of the sun” (grian cloch) in Irish. It has qualities of enhancing whatever it is combined with. Thought. The Meditation and Attunement Stone. Trigonal.