Nickel is a silvery-white lustrous metal with a slight golden shade. It is one of the four ferromagnetic elements that exist around room temperature, the other three being iron, cobalt and gadolinium. Its most vital ore minerals are laterites, including limonite and garnierite, and pentlandite. Enzymes of certain life-forms contain nickel as an active center, which makes the metal a necessary nutrient for those life forms.