Grey, hard, ductile, malleable metal .
In nature, cobalt is found in the Earth's crust, 10-20 ppm, in minerals such as cobaltite, linneaite, smaltite and erytrite . The isotope found in nature is 59Co (100 %, stable) .
In pure solid form, cobalt exist in two forms: hexagonal and cubic form. Of these, the hexagonal form is the most stable form at room temperature