Ni - a hard malleable ductile silvery metallic element that is resistant to corrosion; used in alloys; occurs in pentlandite and smaltite and garnierite and milleritemetal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. garnierite - a green mineral consisting of hydrated nickel magnesium silicate; a source of nickel millerite - a yellow mineral consisting of nickel sulfide; a minor source of nickel pentlandite - a mineral (iron-nickel sulphide) that is the chief ore of nickel smaltite - a gray mineral consisting of cobalt arsenide and nickel; an important source of cobalt and nickel |