Niobium
Melting point – 2468 °C
Symbol – [Nb]
Atomic N° – 41
The largest mines of niobium rich minerals are currently located in Brazil and Canada. Naturally niobium is light grey, lustrous, paramagnetic and has a lower density than other refractory metals.
Niobium oxidises in the earths atmosphere very slowly, hence its application in jewellery as a hypoallergenic alternative to nickel. Niobium has a hardness similar to that of pure titanium and it has similar ductility to iron.
Niobium is considered a technology-critical element. It is used in various superconducting materials, nuclear industries, electronics, optics and jewellery. It becomes a superconductor at cryogenic temperatures and has the highest critical temperature of the elemental superconductors at atmospheric pressure. Niobium has the greatest magnetic penetration depth of any element. In addition, it is one of the three elemental Type II superconductors. Niobium is an effective microalloying element for steel to increase the toughness, strength, formability, and weldability. Niobium is added to glass to obtain a higher refractive index, making possible thinner and lighter corrective glasses.
Tantalum
Melting point – 3017 °C
Symbol – [Ta]
Atomic N° – 73
Tantalum is mined from various regions around the world, with most tantalum coming from South America or Australia. In its natural state, tantalum is dark grey with a bluish tint. As natural sources of tantalum are quickly depleting, experts believe that only about half a century worth of tantalum resources remain.
Tantalum is an inert metal, which means that it does not react to most chemicals and does not dissolve in acid. Due to its biocompatibility, it is hypoallergenic like platinum and is not known to cause allergic reactions or to exacerbate skin conditions. It does not conduct heat and is comfortable and safe to wear. Tantalum jewellery does not scratch or loose shape and is easy to maintain.
Being one of the most durable and rare metals known to man it is used in nuclear reactors, jet engines, rocket nozzles, surgical implants and production of refractive glass. Tantalum is shatterproof and extremely malleable which sets it apart from other contemporary metals.