Rarity is a term that is often overused and readily applied to many aspects of our everyday lives. However, the tangibly rare - that which we can touch, see and feel - exists not only in human experience but in the natural world around us.
These truly rare materials are not man-made and are actually found within Earth's crust.
The likes of aluminium and iron are among the most abundant metals found in Earth's lithosphere and are used broadly in many products and processes. But conversely, what are the rarest metals on our planet? And can these scarce materials be used?
In our latest blog, Austen Knapman will break down and analyse the rarest metals on Earth. But to properly answer this question, and in the interests of practicability and real-world use, we need to look at both the rarest unstable metal and the rarest stable metal out there.
The rarest unstable metal on Earth is the highly radioactive and unusable Francium (Fr). In fact, Francium is so unstable that its longest-lasting radioactive isotope, francium-223, has a half-life of just 22 minutes, making it completely unusable for any human use. In fact, this scarce and highly toxic metal is so rare that it is believed that there is only 30 grams of it present in the entire Earth's crust.
The rarest stable metal on Earth is Tantalum (Ta). Named after Tantalus, a wicked Greek mythological figure who was the son of Zeus, tantalum is an incredibly tough, heavy and hard metal that's blue-grey in colour and the rarest stable element found in our solar system.
Known for its impressive corrosion resistance, chemical inertness and very high melting point, it's an incredibly practical metal for laboratory use as a substitute for platinum and in the manufacturing of medical and dental equipment. Tantalum is also employed in nuclear reactors, aeroplane engines and missile components, and is most frequently used in alloying processes to harden other metals. You may find tantalum in everyday items such as smartphones, DVD players, games consoles and computers.
In physical terms, tantalum averages just 2 parts per million in the Earth's crust and, to date, it's mined in only a few countries such as the Democratic Republic of Congo, Brazil, Rwanda, Nigeria and China.
