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Wolframite

earth science Maturity 7-9 Next article →

Wolframite is a vital mineral used to extract the metal tungsten. It is a tungstate mineral composed of iron, manganese, and tungsten. This mineral belongs to a series that acts as an intermediate between two other minerals. These two ends are called ferberite, which is rich in iron, and hübnerite, which is rich in manganese. Along with the mineral scheelite, the wolframite series provides the most important ores for tungsten.

Stick diagram of wolframite single crystal front view
Stick diagram of wolframite single crystal front view

The chemical makeup of wolframite is a solid solution between its two end members. This means the proportions of iron and manganese can change. A sample can range from 100% ferberite to 100% hübnerite. On average, wolframite contains 60.63% tungsten, 9.21% iron, 9.06% manganese, and 21.10% oxygen. In its pure crystal form, it belongs to the monoclinic crystal system. It can appear in prismatic or lamellar habits, which are specific crystal shapes. The ore itself often looks like a dark grey or reddish black mass.

Wolframite forms through specific geological processes involving heat and pressure. It often forms through magmatic-hydrothermal processes. These processes are associated with felsic magmas, which are types of molten rock. It can also form through metamorphic processes, which happen when rocks change due to intense heat or pressure. You can often find wolframite in quartz veins or pegmatites. These are usually found near granitic intrusives, which are large bodies of igneous rock. It is frequently found alongside minerals like cassiterite, bismuth, quartz, and pyrite.

The history of the name wolframite is quite colorful. In 1546, Georg Agricola used the name "Lupi spuma." This translates from Latin to "wolf's froth" or "wolf's cream." Later, in 1747, Johan Gottschalk Wallerius used the German name "wolf rahm." The name likely refers to how the mineral behaves during extraction. During mining, the mineral consumes large amounts of tin. People compared this to a wolf eating a sheep. The chemical symbol W for tungsten comes from the word "wolfram." The name tungsten itself comes from Swedish words meaning "heavy stone."

Tungsten is a very dense and strong metal with a high melting temperature. Because of these traits, it has many important uses. It is used for electric filaments and armor-piercing ammunition. Hard tungsten carbide is used to make machine tools. In the 19th century, tungsten salts were used to dye cotton and make fire-retardant stage costumes.

Extraction of Tungsten from Wolframite Ore
Extraction of Tungsten from Wolframite Ore

During World War II, wolframite mines were considered strategic assets for making munitions.

Today, tungsten plays a massive role in global industry and chemistry. It is used as a catalyst, which is a substance that helps chemical reactions happen. For example, a hydrocracking catalyst uses tungsten to improve gasoline yields during hydrocarbon refinement. Another use is a De-NOX catalyst. This helps treat nitrogen oxide emissions by converting them into inert N2 gas. Tungsten is also used as a lubricant. Tungsten disulfide (WS2) has a very low coefficient of friction. It can operate in extreme conditions, such as 583 °C in air or 1316 °C in a vacuum.

Tungstic acid
Tungstic acid

The global production and reserves of tungsten are highly concentrated. As of 2022, the world produced 84,000 metric tons of tungsten. China is the leading producer, contributing 71,000 metric tons. Other significant producers include Vietnam, Russia, Bolivia, and Rwanda. The total world reserves are estimated at 3,800,000 metric tons. China holds the largest share of these reserves with 1,800,000 metric tons. Other major reserves are located in Russia, Vietnam, Spain, and Austria. Historically, wolframite was also found in Europe in places like Bohemia, Saxony, and the UK.

While wolframite is useful, its mining has faced ethical challenges. In the Democratic Republic of the Congo, mining practices were linked to the Congo Wars. Because of these issues, wolframite has been considered a conflict mineral. This means the mineral's extraction was tied to unethical or violent situations. Understanding the source of our materials helps us see the full impact of the technology we use every day.

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File:Stick_diagram_of_wolframite_single_crystal_front_view.jpg
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File:Extraction of Tungsten from Wolframite Ore.png
Extraction of Tungsten from Wolframite Ore.png
File:Tungstic acid.jpg
Tungstic acid.jpg
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