The platinum group metals are the heaviest , since they have the highest density. Among them, the most severe are osmium and iridium. This is the hardest material. The density index of these metals is almost the same, except for a slight calculation error.
The discovery of iridium occurred in 1803. He was discovered by the English chemist Smithson Tennat, exploring natural platinum delivered from South America. Translated from the ancient Greek name "iridium" means "rainbow".
It is very difficult to get the hardest metal (iridium), it is almost absent in nature. Often a significant amount of it is contained in meteorites that fell to the ground. According to most scientists, the content on our planet of iridium should have been much larger. But due to the special property of this metal - siderophilicity (similarity to iron), it sank to the very depths of the earth's interior during the formation of the Earth’s core.
Iridium is the hardest metal, which is very difficult to process both thermally and chemically. It does not react with acids, combinations of acids at a temperature of less than one hundred degrees. This metal is subject to oxidation processes when lowered into a solution consisting of a mixture of hydrochloric and nitric acid (aqua regia).
The isotope of heavy metal, iridium-192m2, is of scientific interest as a source of electrical energy, since the half-life of this metal is very large - 241 years. Iridium is widely used in industry and paleontology - it is used for the production of pens for pens, determining the age of the layers of the earth.
The discovery of osmium occurred randomly in 1804. This hardest metal was found in the chemical composition of the sediment dissolved in aqua regia platinum. The name "osmium" comes from the ancient Greek word "smell". In the nature of this metal is almost nonexistent. Most often it is found in polymetallic ore. Like iridium, osmium is almost not subject to mechanical stress. One liter of osmium is much heavier than ten liters of water. But this property of this metal has not yet been used anywhere.
The hardest metal osmium is mined in Russian and American mines. However, South Africa is recognized as its richest deposit. Osmium is often found in iron meteorites.
Of particular interest is osmium-187, exported only by Kazakhstan. It is used to determine the age of meteorites. One gram of this isotope costs 10 thousand US dollars.
The industry mainly uses a hard alloy of osmium with tungsten (osram) for the production of incandescent lamps. Osmium is also a catalyst in the production of ammonia (ammonia). Quite rarely, cutting parts for instruments in surgery are made from this metal.
Both heavy metals - osmium and iridium - are almost always contained in one alloy. This is a certain pattern. And for their separation, you need to make a lot of effort, because they are not as soft as, for example, silver.