Osmium
Osmium has a blue-grey hue and is the densest stable element; it is about twice as dense as lead and slightly denser than iridium. Osmium is a hard but brittle metal that stays shiny even at high temperatures. It has a very low squeezability. Accordingly, its size module is extremely high, reported between 395 and 462 GPa, which is comparable to that of diamond (443 GPa). The hardness of osmium is moderately high at 4 GPa.  Because of its hardness, brittleness, low vapour pressure, and very high melting point, solid osmium is difficult to machine, form, or work.