 Bismuth is a brittle metal with a white , silver @-@ pink hue , often occurring in its native form , with an iridescent oxide tarnish showing many colors from yellow to blue . The spiral , stair @-@ stepped structure of bismuth crystals is the result of a higher growth rate around the outside edges than on the inside edges . The variations in the thickness of the oxide layer that forms on the surface of the crystal causes different wavelengths of light to interfere upon reflection , thus displaying a rainbow of colors . When burned in oxygen , bismuth burns with a blue flame and its oxide forms yellow fumes . Its toxicity is much lower than that of its neighbors in the periodic table , such as lead , antimony , and polonium . 
