hard lead: unrefined lead that is hard because of the impurities it contains
metallic element: any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
lumbosacral plexus: a nerve plexus formed by the ventral divisions of the coccygeal and sacral and lumbar nerves; supplies the lower limbs and perineum and coccygeal area