Lithium be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray as it oxidizes to lithium oxide. While it has one of the lowest melting points among all metals (180 °C), it has the highest melting and boiling points of the alkali metals. Lithium has a very low density (0.534 g/cm), comparable with pine wood. It is the least dense of all elements that are solids at room temperature; the next lightest solid element (potassium, at 0.862 g/cm) is more than 60% denser. Furthermore, apart from helium and hydrogen, it is less dense than
Metallic microlattice lighter still. Tube-based nanostructures are similar structures on a smaller scale. Metallic microlattice A metallic microlattice is a synthetic porous metallic material consisting of an ultra-light metal foam. With a density as low as 0.9 mg/cm (0.00561 lb/ft), it is one of the lightest structural materials known to science. It was developed by a team of scientists from California-based HRL Laboratories, in collaboration with researchers at University of California, Irvine and Caltech, and was first announced in November 2011. The prototype samples were made from a nickel-phosphorus alloy. In 2012, the microlattice prototype was declared one of 10 World-Changing Innovations