Each stone varies. Clear quartz is actually a very programmable stone and is most used in amplification of one's intention, magnification of ambient energies, clearing, cleansing, healing and memory enhancement. This stone can really be programmed to help one with whatever it is they desire since it's such a pure stone of the earth. Clear quartz brings clarity on all levels and can be used to enhance the communications of guides and amplify psychic abilities. It opens all Chakras and energetic pathways throughout the body.
Physically, it stimulates the nervous system and can aid in the growth of hair and fingernails.