Iridium belongs to the platinum group and is white like platinum with a little yellow in it. Iridium is hard and brittle and has a very high melting point, making it difficult to cast and plasticize. The manufacturing process therefore generally uses powder metallurgy. Iridium is the only metal that maintains excellent mechanical properties in air above 1600 °C. Its boiling point is extremely high, ranking 10th among all elements. Iridium exhibits superconducting properties below 0.14 K.

The elastic modulus of iridium is lower than that of osmium and the second highest of all metals. Its high shear modulus and low Poisson's ratio result in high stiffness, making iridium very difficult to process. Although difficult and expensive to produce, iridium has several applications, including strengthening machinery in extreme conditions.
Iridium has the second highest density of all elements, only slightly lower than osmium. Since the density values ??are very similar and measurement is not easy, it was not clear which of the two elements had the higher density. The density value is calculated by atomic weight. The conclusion in 2013 is that the density of iridium is 22.56g/cm3, and the density of osmium is 22.59g/cm3, and the difference between the two is only 0.027g/cm3. However, the atomic weight measurement of osmium still lacks a lot of experimental verification, so it is still impossible to draw a conclusion on which of iridium and osmium has a higher density.