Answer:
Iridium, with atomic number 77 and two stable isotopes, 191 and 193, is formed in a platinum alloy in the regular bar and the weight used for many years to define the meter and the kilogram.
What Iridium is?
Iridium is a very strong, fragile and thick metal and is very rare, too. Iridium is the most corrosion-resistant compound in the Periodic Table of Elements. It has the largest density of all the elements, too. Since it is resistant to deterioration, it is used to set standards for weights and measures.