Chem Explorers

Rare Valuable and Versatile: Uncovering the Secrets of Indium

Indium – A Rare and Useful Element

Have you ever heard of indium? It’s a rare soft metal that’s part of the boron family.

In this article, we will explore its characteristics, discovery, and properties, as well as its uses and importance in various industries.

Characteristics of Indium

Indium is a soft metal that can be easily cut with a knife. It’s part of the boron family, which means that it shares some common characteristics with its neighbors, such as aluminum, gallium, and thallium.

Indium has two stable isotopes, indium-113 and indium-115, with the latter being more common. This rare element occurs in small amounts in ores and minerals, such as sphalerite, which is a zinc ore.

Occurrence of Indium

Indium is a rare element, which makes it difficult to find in large quantities. The primary source of indium is from the byproducts of zinc refining.

Zinc ores and minerals often contain indium, which is separated during the refining process. The amount of indium in zinc ores is typically less than 0.1%, which makes it a precious and valuable metal.

Discovery of Indium

Indium was discovered in 1863 by Heironymous Richter and Ferdinand Reich. They were studying the spectrum of colors emitted by zinc blende using an atomic spectroscope.

They noticed a violet line in the spectrum that they could not identify. After conducting further experiments, they identified the line as being emitted by a new element, which they named indium after its indigo color.

Identification of Indium

The atomic number of indium is 49, and its symbol is In. Its CAS number is 7440-74-6, and it is located in group 13 of the periodic table. Other elements in this group include boron, aluminum, and gallium.

Properties of Indium

General Properties

Indium has an atomic mass of 114.82 g/mol and a molar mass of 114.82 g/mol. Its physical properties include a silvery-white color, a shiny and lustrous appearance, and a relatively low melting/freezing point of 156.6C.

Its boiling point is 2000C, and it has a density of 7.31 g/cm3. Indium’s chemical properties include being able to exist in different oxidation states, such as +1, +2, and +3.

It’s also not very flammable and doesn’t react easily with other elements.

Physical Properties

Indium is a soft metal that is easy to manipulate. It has a silvery-white color and a shiny, lustrous appearance.

Its melting/freezing point is relatively low, which means that it can be easily melted or solidified. It is a solid at room temperature and has a density that is slightly higher than water.

Chemical Properties

Indium is relatively stable and doesn’t easily react with other elements. It can exist in different oxidation states, such as +1, +2, and +3.

It’s not very flammable and doesn’t burn easily. Its chemical properties make it a useful element in various industries, such as electronics and aerospace.

Atomic Data

Indium has 49 electrons, with 2 in the first shell, 8 in the second shell, 18 in the third shell, and 18 in the fourth shell. Its electron configuration is [Kr] 4d10 5s2 5p1.

The valence electrons of indium are located in the 5p orbital, which means that they are available for bonding with other elements. The ionization energy of indium is relatively low, which means that it’s easy to remove one or more electrons from an indium atom.

Uses of Indium

Indium is used in various industries due to its unique properties. Here are some of its uses:

  1. Electronics

    Indium is used in electronic devices, such as LCD screens, touchscreens, and solar panels. It’s used as a transparent and conductive coating on these devices.

  2. Aerospace

    Indium is used in aerospace applications, such as the production of turbine blades.

    It’s also used as a coating on aerospace vehicles, such as space shuttles.

  3. Medical

    Indium is used in some medical applications, such as imaging and cancer treatment.

  4. Alloys

    Indium is often used as an alloy with other metals, such as silver, gold, and platinum. These alloys can be used as dental fillings, electrical contacts, and other applications.


In conclusion, indium is a rare and valuable element that has unique properties that make it useful in various industries. Its characteristics, discovery, and properties have been discussed in this article, as well as its uses.

As technology advances, the demand for indium is likely to increase, which will make it even more important. Indium is an essential metal used for different purposes, ranging from electronics to aerospace.

Its unique characteristics have made it an ideal choice for manufacturers across a variety of industries. In this article, we will explore some of the most common uses of indium, such as in high-speed motors, coatings, transistors, and medical applications.

We will also discuss the potential toxicity of indium and its compounds and the risk they pose to human health.

Uses of Indium

High-Speed Motors

One of the most common uses of indium is in high-speed motors. It is often used in ball bearings due to its ability to reduce friction and improve the longevity of the ball bearing.

Indium is also used in lubricating oil to improve its performance and lower oxidation rates. Its singular properties of low surface energy, high elasticity, and excellent corrosion resistance help to reduce contact fatigue and ensure wear-resistant surfaces.

These properties increase the quality and efficiency of high-speed motors, making them more reliable and long-lasting.


Another way indium is frequently used is in coatings. Indium’s unique properties make it an essential substance in coatings that prevent tarnishing of mirrors, and in protective films applied to delicate parts that need to be shielded from environmental factors.

Indium coatings are also used in fire sprinkler systems to prevent oxide buildup and prevent corrosion on the insides of pipes. This helps in maintaining the effectiveness of fire-fighting systems and keeps them running over time.


Indium can be used as germanium doping in transistors, improving their electrical conductivity. Doping is the process of adding impurities to pure semiconductor materials to produce a conductivity that is greater than that of pure silicon or germanium.

The doping process often used in the manufacture of transistors creates p-type or n-type semiconductors, which work by controlling the flow of current between them. Indium doping helps to increase the speed and sensitivity of electronic devices by improving their conductivity.

Medical Applications

Indium is also used in certain fields of medicine. Radioimmunoscintigraphy, a diagnostic method that uses a radioactive chemical attached to an antibody to locate specific antigens or proteins in the body, makes use of indium.

For example, a radioactive indium compound called In-DTPA-octreotide is used to locate neuroendocrine tumors in the body. Additionally, indium is sometimes used to treat prostate cancer and bone abscesses.

A substance called In-Cl3, a radioactive isotope of the element, can be used to locate infections in bone abscesses. Indium-based radiopharmaceutical compounds have proved useful in the medical industry because of their unique properties such as precise target detection and low toxicity.

Toxicity of Indium

While indium is a useful element that has many applications, exposure to indium in its compounds can be dangerous for humans. According to some animal studies, ingestion of indium over a prolonged period can cause lung cancer.

Indium compounds used in different applications, such as indium tin oxide, indium phosphide, and indium arsenide, have also been linked to some toxic effects, including liver and kidney damage, lung damage, and fibrosis. When indium compounds are ingested, they can accumulate in the bones and liver, causing long-term toxicity.

Furthermore, although the toxic effects might not be immediately noticeable, chronic exposure to indium can eventually cause diseases such as indium lung disease, which has been observed in workers who have been exposed to indium dust. The earliest identified case of indium lung disease was in Japan, where a large percentage of employees in the electronic industry were exposed to indium.


In conclusion, indium is a valuable metal that possesses unique properties, making it ideal for various applications in different industries. It’s a vital component in high-speed motors, coatings, and transistors, and has proved useful in medical applications such as radioimmunoscintigraphy and cancer treatment.

However, indium compounds can have toxic effects when ingested or inhaled over prolonged periods. While the use of indium in various industries is not necessarily harmful, appropriate safety measures should be considered, and its risks and precautions should be taken seriously.

Indium is a rare and valuable metal that has various unique properties, making it a useful tool in different fields of engineering, science, and medicine. In this article, we will explore some interesting facts about indium and discuss its cost per kilogram, and how it is priced in the market.

Interesting Facts about Indium

Crystal Twinning

One of the interesting properties of indium is crystal twinning. Crystal twinning occurs when two or more crystals grow together in a symmetrical configuration.

In the case of indium, twinning creates a characteristic “herringbone” pattern, which is commonly visible on the surface of indium sheets and foils. Twinning is common in metals, minerals, and rocks, but the pattern it produces on indium is striking and easy to recognize.


Another fascinating thing about indium is that it produces sound when bent. When indium is bent or flexed, it emits a distinct sound that is similar to a tapping sound.

This sound occurs due to the vibration and movement of indium atoms. The sound is not as prominent as that produced by other metals such as steel, but it is still a unique characteristic of this rare metal.

Indium Cost

Indium is a rare metal that is not commonly found in the earth’s crust. It often occurs in small quantities and is typically obtained as a byproduct of other mining activities.

This makes its cost per kilogram high compared to other metals like copper and aluminum. Indium’s price fluctuates often, and it is usually traded on the metal exchange markets.

Metal Price

The price of indium is determined by various market factors, such as supply, demand, and production costs. Its rarity is one of the significant reasons why indium commands a high price in the metal market.

In 2020, the indium price ranged from about $3300 to $3500 per kilogram, a lesser cost compared to previous years. Its price hit an all-time high of $1,200 per kilogram in 2006 because of its use in flat-screen TVs and other electronics.

The metal’s skyrocketing price led to its substitution by more affordable materials like silver and copper. The price then stabilized to about $600 per kilogram between 2009 and 2016.

Cost Per Kg

The cost of indium is spread across various industries due to its many applications, including its use in the aerospace and defense sectors, as well as in cryogenics and medical devices. The cost per kilogram of indium depends on the level of purity, availability, and demand from different industries.

Some sectors pay more for indium than others due to its critical role in their operations. For example, the medical industry uses radiopharmaceutical compounds made using indium, and the aerospace sector uses it in alloys that are lightweight and corrosion-resistant, which drives up the cost per kilogram significantly.

Indium is an essential metal across different sectors, its numerous applications and unique properties make it a valuable asset, and its price is a reflection of its scarcity and usefulness. While the metal’s price can fluctuate frequently, its varied applications make it a vital component in multiple industries, and the high demand for indium will likely continue for years to come.


In conclusion, indium is a rare and valuable metal with unique properties that make it essential in various industries. Its uses range from high-speed motors and coatings to transistors and medical applications.

Interestingly, indium exhibits crystal twinning and produces sound when bent. However, its cost per kilogram is relatively high due to its scarcity and demand.

Overall, indium plays a crucial role in technological advancements and offers potential benefits in fields such as medicine. Remember, while its applications are significant, caution should be taken regarding potential toxicity when dealing with indium compounds.


  1. What are the unique properties of indium?

    Indium exhibits crystal twinning and produces sound when bent.

  2. How much does indium cost per kilogram?

    The cost of indium fluctuates based on supply, demand, and production costs, but it is generally higher than other metals due to its rarity.

  3. What are the main uses of indium?

    Indium is used in high-speed motors, coatings, transistors, and medical applications.

  4. Is indium toxic?

    Indium compounds can be toxic, especially when ingested or inhaled over a prolonged period, so proper safety measures are essential.

  5. Why is indium considered valuable?

    Indium’s scarcity, unique properties, and wide range of applications contribute to its value in various industries.

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