In the shape lies the magick! Round stones symbolize the receptive powers of the universe, of magnetism and the Mother Goddess. They are linked with the female reproductive system and indeed can be used to represent women in, for instance, healing rituals. These stones are keys to spirituality, to unfolding psychic awareness. They are used in love spells and in all manner of 'attraction' rituals. An example: to attract money, place small pieces of olivine or jade in a square surrounding the round stone and visualize.
Spheres, now available in a wide range of stones, are often used in scrying sessions. Long, thin stones are obvious phallic symbols, though this doesn't necessarily include quartz crystals or other crystalline stones. They are projective and represent electricity and the Great God of Pagan religions. These are energy stones and can be carried or placed on the altar for this purpose. For protection hang one on the front door or place before a mirror.
Round and long stones can be used in conjunction for love spells by placing them beside or on top of each other on the altar while visualizing. Placing other love-attracting stones nearby, or surrounding the two, furnishes additional power and symbolism to the ritual.
Stones that are egg-shaped are used to stimulate creativity and fresh ideas. They are also placed on the stone altar to bring 'fertility' to the ritual. In the past, small stones of this shape were carried by women to promote conception. Larger ones can be buried in the garden for fertile plants.
Square stones symbolize the Earth, prosperity and abundance, and so are used in spells of this type. They also promote stability and grounding. Use one of these to concentrate on one project at a time if you feel that your life is too scattered.
Heart-shaped stones are, of course, used magickally to stimulate or draw love. They can be carried to bring love into your life or to magnify the love within, to allow yourself to receive and give love.
Triangular stones are protective and are worn or carried for this purpose. To guard your home, place a triangular stone in the window facing the nearest street.
Stones which are found in L-shapes are thought to bring good fortune,perhaps because this form suggests the conjunction of the spiritual with the physical. They can be carried as good luck pieces or placed on the altar.
Stones that resemble parts of the body are used in magick to heal or strengthen that particular part: kidney-shaped ones for the kidneys,and so on. These graphic stones, which are worn after the ritual, are focal points for visualization.
Pyramid-shaped stones, rare in nature but increasingly common among dealers, concentrate and release energies up through the tip toward the magickal goal. Thus, if you need money, you might put a dollar bill beneath the pyramid and visualize money energy flowing from the bill up through the pyramid and out to bring you prosperity.
Diamond-shaped stones obviously recall that precious gem and so are used to attract riches.These examples should be sufficient to allow you to explore the possible magickal uses of the shaped stones you may find on beaches,river banks or in dry creek beds.
[Encyclopedia of Crystal, Gem, and Metal Magic-Scott Cunningham]