Gallium was discovered in 1875 by the French chemist Paul-Émile Lecoq de Boisbaudran. Earlier, the Russian chemist Dmitri Ivanovich Mendeleev had predicted the existence of an element that would lie between aluminum and indium in the periodic table. This then-undiscovered element was referred to as eka-aluminum. In honor of his homeland, Lecoq de Boisbaudran named his discovery gallium.

Gallium remained largely unnoticed for a long time because it could not be economically extracted from ores. Due to its poor availability and the resulting high price, interest in gallium and its chemistry was limited.

Interest in the element grew with the discovery of the semiconductor properties of gallium compounds.

In 2024, the estimated global consumption of gallium was around 600 tons per year. The main consumer is the electronics and semiconductor industry.

About three-quarters of the gallium is used for the production of gallium nitride (GaN) and gallium arsenide (GaAs) wafers. GaAs and GaN outperform silicon as semiconductor materials in terms of speed, heat resistance, and energy efficiency.

GaAs wafers are used in 5G and 6G mobile communication chips, satellite and radar systems, and in optoelectronics (LEDs, laser diodes, solar cells).

Fast chargers, inverters for electric vehicles, data centers, fiber optics, and defense systems such as radars use GaN semiconductors.

Smaller amounts of gallium are also used in medicine and research.

Gallium is produced as a byproduct of aluminum and zinc production. Therefore, bauxite and sphalerite are the most important minerals. China’s monopoly on gallium is particularly noticeable, as the country controls between 80 and 95 percent of global production. The leading gallium producers are China Germanium, a subsidiary of Yunnan Chihong Zinc & Germanium, and the state-owned aluminum company Chinalco.

Until 2015, the Germany-based company Ingal Stade was the largest gallium producer outside of China. However, the operation was shut down in 2016.

Liquid crystals made from organic compounds are used as a gallium substitute in LEDs for optical displays.

Complementary metal-oxide-semiconductor (CMOS) power amplifiers based on silicon compete with GaAs power amplifiers in mid-range third-generation (3G) mobile phones.

Indium phosphide components can replace GaAs-based infrared laser diodes in some applications with specific wavelengths, and helium-neon lasers compete with GaAs in applications with visible laser diodes.

Silicon is the main competitor to GaAs in solar cell applications.

In many defense-related applications, GaAs- and GaN-based circuits are used due to their unique properties, for which there are no effective substitutes.

Cobalt compounds have been used for thousands of years to give glazes and ceramics a blue color. They have been found in Egyptian statuettes and Persian necklace beads from the 3rd millennium BC, in glass artifacts in the ruins of Pompeii, and in China during the Tang Dynasty (618–907 AD) as well as later in the blue porcelain of the Ming Dynasty (1368–1644).

In the Middle Ages, miners considered these compounds valuable but cursed silver ores because they smelled like garlic during smelting due to their arsenic content and could not be reduced. These ores were therefore called kobolds, nickel, or wolf’s spit. In 1735, the Swedish chemist Georg Brandt succeeded in isolating the metal. He recognized it as a new element and named it cobalt.

Today, cobalt is primarily used in lithium-ion batteries, especially in electric vehicles, but also in smartphones, laptops, and other electronic devices. About 60 percent of cobalt demand comes from the battery sector. Electric cars are the main driver of increasing cobalt mining.

Cobalt is an important component of the cathode in lithium-ion batteries. The metal provides stability and a high energy density in the batteries, which is crucial for the range of electric vehicles.

Other applications of cobalt include superalloys for engines, gas turbines, and industrial machinery.

In combination with tungsten and carbon, cobalt forms a hard metal (e.g., tungsten carbide-cobalt), which is used in cutting tools, drills, and mining machinery.

Cobalt is also used in permanent magnets (e.g., aluminum-nickel-cobalt and samarium-cobalt magnets), which play an important role in motors, sensors, and wind turbines.

Furthermore, cobalt is used in catalysts, pigments for the production of paints, ceramics, and glass, as well as in very small amounts in medical products such as joint prostheses and dental alloys.

Cobalt ore is usually obtained as a byproduct during the mining of iron, nickel, copper, silver, manganese, zinc, and arsenic ores. The most important cobalt-containing minerals include cobaltite, heterogenite, spherocobaltite, erythrite, carrollite, and skutterudite, although these are relatively rare.
Currently, the largest amounts of cobalt come from the Central African “Copper Belt.”

About three-quarters of the world’s cobalt supply originates from the Democratic Republic of Congo (DRC), where the largest cobalt mines in the world—Tenke Fungurume and Kamoto—are located. The biggest producer of refined cobalt is China, which imports vast quantities of cobalt ore from the DRC.

Other important sources are sulfide deposits in Russia, Canada, and Australia. Recently, laterite ores in tropical regions such as Indonesia, the Philippines, and New Caledonia have gained in importance.

Indonesia is developing into another key country for cobalt mining.

Among the largest companies are the Chinese CMOC Group (China Molybdenum), operator of the Tenke Fungurume mine. The Swiss company Glencore follows in second place, owning the Kamoto and Mutanda mines in the DRC.

Approximately ten percent of cobalt demand is met through recycling.

Depending on the application, replacing cobalt can lead to performance losses or higher costs. In lithium-ion batteries, the world’s leading use of cobalt, the cobalt content is being reduced. In China, cobalt-free lithium iron phosphate batteries hold a significant market share.

Possible substitutes in other applications include barium or strontium ferrites, neodymium-iron-boron alloys, or nickel-iron alloys in magnets. Cerium, iron, lead, manganese, or vanadium are used as cobalt replacements in pigments.

Iron, iron-cobalt-nickel alloys, nickel, ceramic-metal composites (cermets), or ceramics are applied in cutting and wear-resistant materials.

Nickel-based alloys or ceramics replace cobalt in jet engines. In petroleum catalysts, nickel can substitute for cobalt, and titanium-based alloys are an alternative in prosthetics.

Crocoite (red lead ore) was one of the first chromium minerals to be discovered. In Persia and during the Qin Dynasty in China, it was used to produce pigments for bright yellow-orange colors in ceramics. Chromium oxide green has been used for centuries to color glass or enamel. Vincent van Gogh, for example, used "chrome yellow" in his famous Sunflowers series, which includes a total of seven paintings.

In 1761, German mineralogist Johann Gottlob Lehmann analyzed a red-orange mineral from Siberia, later identified as crocoite. In 1797, French chemist Nicolas-Louis Vauquelin isolated chromium oxide and, by heating it with carbon, obtained chromium metal. Pure chromium was first produced in 1894 by Hans Goldschmidt using the aluminothermic process. The simpler carbon reduction previously used by Vauquelin also produced chromium carbide alongside the metal.

At the beginning of the 19th century, chromium compounds were used in dyes, paints, and tanning agents.

In the 1820s, chromium plating (electroplating) was developed to improve the durability and shine of metals. By the end of the 19th century, it was discovered that adding chromium to iron produced stainless steel. Since then, chromium has been an essential component in stainless steel products such as cutlery, machinery, and construction materials.

During World War II, chromium was considered a strategic material for armor plating, aircraft engines, and weapons. In the post-war era, chrome plating became widespread in automotive parts (bumpers, trim) and household items.

Due to the presence of toxic hexavalent chromium (Cr⁶⁺) in industrial waste, chromium poses a significant environmental risk.

About 45.000 tons of chromium are mined annually.

The majority is used in the metallurgical industry. Approximately 70 percent of chromium goes into stainless steel products alone. Other applications in the metal industry include iron alloys (ferrochromium) used in steel production to increase strength and corrosion resistance. Chromium is also a component of superalloys and tool steels for jet engines and gas turbines.

On chrome-plated faucets, bumpers, and motorcycle parts, the metal provides shine, corrosion resistance, and protection against wear.

Chromium oxide serves as a pigment for green shades in paints, ceramics, and glass, as well as a refractory material, for example in heat-resistant bricks for furnaces. Chromite is also added to bricks and stones to make them fireproof.

Although chromium compounds cover the entire color spectrum, only a few of them are used as pigments.

China is the leading producer of ferrochromium and stainless steel, as well as the largest consumer of chromium.

90 percent of the chromium mined worldwide comes from chromite deposits. Other chromium minerals include crocoite, uvarovite, eskolaite, and chromdiopside.

Global resources amount to over 12 billion tons of chromite, enough to meet demand for centuries. Geographically, 95 percent of the world’s chromium deposits are concentrated in Kazakhstan and Southern Africa.

The largest chromium producers include South Africa, India, Kazakhstan, and Turkey.

The largest active chromium mine in the world is the Kemi Mine in Finland, operated by the Finnish steel producer Outokumpu.

The world’s largest chromite deposit is the Bushveld Complex in South Africa.

Chromium is irreplaceable for its most important applications, neither in stainless steel nor in superalloys.

Chromium-containing scrap can substitute for ferrochrome in some metallurgical applications.

Limestone has been used for tens of thousands of years. Crushed limestone was already used as a pigment (white chalk) in prehistoric cave paintings. Lime mortar was used in constructions as early as 10.000 BC in Mesopotamia and in ancient Egypt. The outer walls of the Great Pyramid of Giza (around 2600 BC) were made of Tura limestone. The ancient Romans used lime concrete in the construction of the Pantheon.

The name “Calcium” is derived from the Latin word calx. The Romans used this term to denote lime, limestone, chalk, and mortar made from lime.

The silvery, relatively soft and light metal was first isolated in 1808 by Sir Humphry Davy, after he distilled mercury from an amalgam produced by the electrolysis of a mixture of lime and mercury oxide.

The most commonly used calcium compound across various industries is calcium carbonate, also known as limestone, which is inexpensive and versatile.

It is the main component of the most important building materials: cement, mortar, and concrete. Calcium carbonate is used in the paper industry as a filler or coating to achieve smoothness and brightness. In agriculture, limestone is used to improve acidic soils.

Calcium oxide, also known as quicklime, is produced by heating the raw material calcium carbonate. Calcium oxide is used in steel production, water treatment, and chemical manufacturing.

Calcium hydroxide (slaked lime) is used in wastewater treatment, leather tanning, and mortar production.

Calcium sulfate (gypsum or plaster) is another application in the building materials industry. Calcium chloride is used in road de-icing agents, food preservatives, concrete accelerators, and drying agents.

Pure calcium metal is used as an alloying element for aluminum, copper, lead, magnesium, and other base metals, as a deoxidizer for certain high-temperature alloys, and as a getter in vacuum tubes.

The production volumes of calcium metal are relatively low compared to other metals, ranging from 10.000 to 20.000 tons annually.

Calcium is a very abundant element in the Earth’s crust and occurs in numerous minerals, many of which are economically significant.

The most common sources of calcium are carbonate minerals such as calcite, found in limestone, marble, and chalk. Calcium is also present in sulfate minerals like gypsum and anhydrite, in phosphate minerals such as apatite, and in silicate minerals including wollastonite, plagioclase feldspar, and grossular.

The main producing countries of calcium metal are China, Russia, France, and the USA.

Limestone (calcium carbonate) is a substitute for lime (calcium oxide) in many applications, such as agriculture, flux production, and sulfur removal. Limestone contains fewer reactive substances, reacts more slowly, and may have additional disadvantages compared to lime depending on the application. However, limestone is significantly cheaper than lime.

Calcined gypsum is an alternative material for industrial plasters and mortars.

Cement, cement kiln dust, fly ash, and lime kiln dust are potential substitutes for some construction applications of lime.

Magnesium hydroxide is a substitute for lime in pH regulation, and magnesium oxide is a substitute for dolomitic lime as a flux in steel production.