Tungsten, also known as wolfram, is a rare and versatile metal. In nature, tungsten is found in ore form, combined with other elements. While it's first isolated as an element in the late 18th century, use of wolframite, its ore, goes back further.
Ancient Egyptians use a mineral, now called wolframite, to create yellow pigment for pottery and glass. The first known use of tungsten is in ancient China, where it's incorporated into porcelain glazes by the 8th century BCE.
The most common tungsten ores are wolframite (FeMnWO4) and scheelite (CaWO4). These ores are crucial sources of tungsten and mined in different parts of the world. The name "tungsten" comes from the Swedish "tung sten," meaning “heavy stone.”
Tungsten forms in a combination of geological processes, including igneous and hydrothermal activities. High temperatures and pressures form different tungsten minerals. In the magmatic segregation process of formation, it crystallizes from a molten state in the mantle of the Earth.
Over millions of years, tectonic movements bring minerals closer to the earth's surface, where they are mined. The extraction of tungsten from the ground involves mining and milling to obtain the raw material necessary for further processing.
Properties of Tungsten
Tungsten is one of the most valuable metals on the periodic table. Some distinguishing characteristics include:
High Melting Point: Tungsten has the highest melting point of all metals (3422°C), making it ideal for high-temperature applications.
Density: It is extremely dense (19.3 g/cm³), contributing to its use in applications where weight and stability are critical.
Hardness: Tungsten is one of the hardest metals, providing durability in wear applications.
Although tungsten is a hard metal it's brittle and prone to shattering, which makes it unsuitable for everyday wear, as in jewelry. It's commonly used to manufacture cutting tools, electrical contacts, and radiation shielding.
Two primary mining methods are used: open-pit and underground mining. Open-pit mining involves removing layers of soil and rock to reach the ore deposits, used for shallow ores.
In contrast, underground mining is used for deeper ores, involving tunnels and shafts to reach tungsten deposits. After extraction, the ore undergoes a series of physical and chemical processes to isolate the tungsten.
This often involves crushing the ore, grinding it, and using gravity separation, flotation, or magnetic separation before it is roasted to oxidize the tungsten. The resulting tungsten oxide is then reduced to produce metallic tungsten.
The most common method for recycling tungsten from scrap is the hydrometallurgical process. This includes dissolving the material in leaching agents such as sodium hydroxide, followed by precipitation and purification steps to isolate the tungsten.
This recycling process is crucial due to tungsten's established value and scarcity. As sustainability becomes a priority in metal sourcing, recycling of tungsten from alloys gains visible importance.
Tungsten deposits are rare. Major tungsten producers include China, Russia, Portugal and Canada. Significant tungsten ore deposits are often found in granitic rocks, skarns, and alluvial deposits. China produces about 75% of the world's tungsten.
Relationships with Other Metals
Tungsten has unique relationships with several metals in alloys. Combined with steel it creates tungsten carbide, a very hard metal widely used in industrial cutting tools and abrasive applications.
Alloyed with iron and other metals, tungsten enhances their hardness and thermal stability. This is valuable in aerospace, military, and industrial applications.
Ancient and Medieval Uses
Historically, tungsten is used in pigments and added to various metal mixtures to enhance their properties. Due to its extreme melting temperature and brittle nature it can be difficult to work with. It's found at Uraniborg, the observatory of famed astronomer and alchemist Tycho Brahe (1546 - 1601)
Wolframite is used to make tungstic acid, or hydrated forms of tungsten trioxide, WO3. To produce tungstic acid, strong acids are used to treat solutions of alkali metallic tungstates (tungsten / oxygen salts).
Another method involves the reaction between sodium tungstate and hydrogen carbonate. Tungstic acid has the formula H2WO4 or H2O4W. It's heat stable and insoluble in water and most organic solvents.
Pure tungstic acid can also be derived by reacting pure tungsten with hydrogen peroxide. These methods produce a brilliant yellow pigment. Tungstic acid is used as both a mordant and dye for fabrics
Uses Today
Today, tungsten serves numerous modern applications:
Electronics: Tungsten is used in filaments for incandescent bulbs and as contacts in electrical applications due to its thermal and electrical conductivity.
Medical Equipment: Its high density makes tungsten ideal for radiation shielding in medical X-ray and cancer treatment devices.
Aerospace and Defense: Tungsten is employed in armor-piercing ammunition and high-performance aerospace components, benefiting from its strength and high melting point.
Jewelry: Tungsten carbide's hardness makes it an attractive option for wedding bands and fashion accessories.
Facts About Tungsten
Symbol: Tungsten's chemical symbol is "W," derived from its alternate name, wolfram.
Heavy Metal: It is the heaviest non-radioactive element, giving it unique applications in various industries.
Strings of Steel: It is used to make guitar strings due to its durability, providing longevity and resilience against wear.
Superhero Material: Tungsten features in several comic book heroes' stories, often referenced for its unbeatable attributes. It's the strongest metal in the world.
Tungsten has the lowest vapor pressure of all metals, allowing it to retain its strength and stability at high temperatures.
The Wolfram Crisis (1943)
The diplomatic conflict known as the Wolfram Crisis (Crisis del wolframio in Spanish) occurred during World War II between Francoist Spain and the Allied powers. This conflict arose due to efforts to prevent Spanish exports of tungsten ore to Nazi Germany.
Tungsten is crucial for anti-tank weapons and machine tools. Most of Europe's wolframite mines, including the Barruecopardo, are in northwest Spain and north Portugal. Demand for this strategic mineral during wartime causes a price surge, as Spain drives up profits.
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