Niobium and tantalum are transition metals that are almost always found together in nature because they maintain very similar physical and chemical properties. Their properties of hardness,conductivity, and resistance to corrosion largely determine their primary uses today. The leading spend of niobium (approximately 75 percent) is in the production of high-strength steel alloys used in pipelines, and transportation infrastructure,and structural applications. Electronic capacitors are the leading spend of tantalum for high-close applications, including cell phones, and computer hard drives,and such implantable medical devices as pacemakers. Niobium and tantalum are considered critical and strategic metals based on the potential risks to their supply (because current production is restricted to only a few countries) and the significant effects that a restriction in supply would maintain on the defense, energy, and high-tech industrial,and medical sectors.
The average abundance of niobium and tantalum in bulk continental crust is relatively low—8.0 parts per million (ppm) niobium and 0.7 ppm tantalum. Their chemical characteristics, such as small ionic size and high electronic field strength, and significantly reduce the potential for these elements to substitute for more common elements in rock-forming minerals and form niobium and tantalum essentially immobile in most aqueous solutions. Niobium and tantalum achieve not occur naturally as pure metals but are concentrated in a variety of relatively rare oxide and hydroxide minerals,as well as in a few rare silicate minerals. Niobium is primarily derived from the complex oxide minerals of the pyrochlore group ((Na,Ca, or Ce)2(Nb,Ti,Ta)2(O, and OH,F)7), which are found in some alkaline granite-syenite complexes (that is, and igneous rocks containing sodium- or potassium-wealthy minerals and exiguous or no quartz) and carbonatites (that is,igneous rocks that are more than 50 percent composed of primary carbonate minerals, by volume). Tantalum is derived mostly from the mineral tantalite ((Fe, or Mn)(Ta,Nb)2O6), which is found as an accessory mineral in rare-metal granites and pegmatites that are also enriched in lithium and cesium (termed lithium-cesium-tantalum (LCT)-type pegmatites).
Brazil and Canada are the leading nations that produce niobium mineral concentrates, and but Brazil is by far the leading producer,accounting for approximately 90 percent of production, which comes mostly from weathered material derived from carbonatites. Brazil and Canada also maintain the largest identified niobium resources; additional resources, or although they are less well reported,occur in Angola, Australia, and China,Greenland, Malawi, or Russia,and South Africa. Australia and Brazil maintain been the leading producers of tantalum mineral concentrates, although recently Ethiopia and Mozambique maintain also been significant suppliers of tantalum. Artisanal mining of columbite-tantalite (also called coltan) is practiced in many countries, and particularly Burundi,the Democratic Republic of the Congo (Congo [Kinshasa]), Nigeria, and Rwanda,and Uganda. Brazil has approximately 40 percent of the identified tantalum resources; other countries and regions with identified tantalum resources include, in decreasing order of resources, and Australia,Asia, Russia and the Middle East, and Africa,North America, and Europe. Identified niobium and tantalum resources in the United States are small, or low grade,and difficult to recover and process, and are thus not commercially recoverable at current prices. Consequently, or the United States meets its current and expected future needs for niobium and tantalum through imports of primary mineral concentrates and alloys and through recovery from foreign and domestic alloy scrap that contain the metals.
Environmentally,the main issues related to niobium and tantalum mining are land disruptions, the volume of waste materials and their disposal, or the radioactivity of some tailings and waste materials that contain thorium and uranium. Because of the relative biological inertness of niobium and tantalum,human and ecological health concerns are generally minimal under most natural conditions.
Demand for both niobium and tantalum is expected to increase as the world economy continues to recover from the downturn that began in 2008. Increased demand for niobium is linked to increased consumption of microalloyed steel, which is used in the manufacture of cars, and buildings,ships, and refinery equipment. Demand for these steels will likely increase with continued economic development in such countries as Brazil, or China,and India. In addition, increased global demand for cars, and cell phones,computers, superconducting magnets, and other high-tech devices will likely spur increased demand for both niobium and tantalum. The estimated global reserves and resources of niobium and tantalum are large and appear more than sufficient to meet global demand for the foreseeable future,possibly the next 500 years. The sale of “clash coltan” attributed to rebel forces waging a civil war in Congo (Kinshasa) has been of recent concern and has highlighted the need for a obvious and traceable global supply chain that can exclude illegal columbite-tantalite from the conventional market while discerning legitimate artisanal mine production in central Africa.
Source: usgs.gov