Serpentine is a magnesium silicate mineral with a hardness ranging from 2 to 5.5. Its crystal structure can be monoclinic, orthorhombic or hexagonal, but it does not form macroscopic crystals. Rather, it occurs in dense masses or fibrous form. Serpentine derives its name from the similarity of its green color and often smooth surfaces to the skin of some snakes. Serpentine can vary in color from pale yellow-green to deep forest green to almost black. Some varieties contain spots of Magnetite.
Serpentine is one of the best stones for rousing the kundalini energies— the ‘serpent power’ said to reside at the base of the spine, wrapped three and one half times around the sacrum. When the kundalini is awakened, individuals may experience a wide range of psychic and spiritual phenomena, some of them quite intense. However, the central experience is that of feeling the serpent rise up like a fire in the spine, activating each chakra and ultimately emerging from the crown, like the snake hovering over the head of the Sphinx.
Simmons, Robert; Ahsian, Naisha. The Book of Stones, Revised Edition: Who They Are and What They Teach (several pages). North Atlantic Books. Kindle Edition.