The most naturally occurring densest element on earth is Osmium (Os). The name is derived from the Greek word ‘Osme’ meaning smell. It is a very hard and bluish-white metal. Its atomic number is 76. It is the least abundant stable element in earth’s crust and is found in ores containing platinum. South Africa is the largest producer followed by Russia and then Canada. It is insoluble in most acids.
It has a blue-gray tint. It is slightly denser than iridium. X-ray diffraction data is used for calculation of density. Iridium has a density of 22.562±0.009 g/cm3 while that for osmium is 22.587±0.009 g/cm3 .
The metal is not used in its pure state due to its volatility and toxicity. The metal alloys with platinum group metals like iridium, platinum etc. Osmium platinum alloys are very hard and have high melting points. Osmium tetroxide (OsO4), an important compound of the element is an oxidizing agent. It is a volatile liquid and has very strong chlorine like odor.
It is hard but brittle. Even at high temperature, it remains lustrous. Solid osmium is difficult to machine, form or work due to its hardness, brittleness and high melting point. Osmium tetroxide is used in making nibs of fountain pen, in armor piercing shells, record player needles, finger prints detection, electrical contacts and few other applications.