Scandium (Sc)

Where Found

Scandium is a transition element that is usually dispersed in minerals, and the only minerals in which it is concentrated are quite rare. It is difficult to extract from minerals and is usually mined as a by-product from mining other elements from some uranium deposits and from some iron-rich basic-to-ultrabasic igneous rocks—less than 52 weight percent silica (SiO₂)—or the weathered products from these rocks.

China, Kazakhstan, Russia, and Norway are producers of scandium. It is mostly mined and processed at Zhovti Vody, Ukraine, which has about 7 million metric tons of ore with 1.4 grams per metric ton of scandium. Some scandium has also been produced in the United States at Darby, Montana.

Primary Uses

Scandium is used in small amounts to strengthen metal products such as aluminum in baseball bats, lacrosse sticks, and bicycle frames. It also has been used in lighting, since scandium makes light appear to be the color of sunlight. Scandium has been used in lasers and aerospace applications as well.

Technical Definition

Scandium (abbreviated Sc) is a metal similar in properties and abundance to the rare earth elements (the lanthanide series). The element is difficult to separate from the other constituents in a mineral. It has never been found as a pure, uncombined element.

Scandium is a silvery-white metal with a density of 2.99 grams per milliliter at 25° Celsius. It has a boiling point of 2,700° Celsius and a melting point of 1,541° Celsius. It has an atomic number of 21 and an atomic weight of 45 grams per mole. Scandium normally has an oxidation state (charge) in a compound of plus three.

Description, Distribution, and Forms

Because scandium is so dispersed in minerals, there have been no large deposits of the element mined. Minerals containing scandium are extremely rare. These minerals include thortveitite, (Sc,Y)₂Si₂O₇; bazzite, Be₃Sc₂Si₆O₁₈; kolbeckite, ScPO₄H₂O; cascandite, Ca(Sc,Fe)Si₃O₈(OH); and jervisite, (Na₂,Ca,Fe) (Sc,Mg,Fe)Si₂O₆. Scandium has been mined almost entirely from the ores or mine tailings of other elements, such as titanium, uranium, zirconium, iron, and aluminum. Some of these deposits formed in igneous rocks (from molten rock material), contact metamorphic rocks (altered solid rocks changed because of contact with molten rock material), hot water deposits, recent weathering, recent stream deposits, and sedimentary rocks.

Igneous rocks containing the most scandium are found in iron and titanium minerals in basic and ultrabasic rocks such as ilmenite (less than 0.015 percent), pyroxene (less than 0.03 percent), and titanium-rich magnetite (less than 0.002 percent). Contact metamorphic rocks usually contain low scandium contents, although, in Kazakhstan, a few minerals such as iron-rich muscovite and beryl have been found to contain up to 0.4 percent scandium. Some high-scandium minerals have been found in hot water deposits in Utah. These include beryl (0.3 percent), hematite (0.1 percent), and brucite (0.5 percent). weathering deposits and stream deposits formed from basic and ultrabasic rocks that were mined for titanium and zirconium contain scandium in minerals like leucoxene, ilmenite, and anatase (less than 0.01 percent). bauxite (aluminum-rich ore formed by weathering) formed on ultrabasic to basic rocks in the Ural Mountains in Russia contains less than 0.01 percent scandium. Also, sedimentary iron ores formed on basic to ultrabasic rocks and some uranium ores may contain up to 0.01 percent scandium. Such uranium ore deposits have been found in sandstones in the Colorado Plateau of the United States and in conglomerates in Canada and South Africa.

History

In the nineteenth century, Dmitry Ivanovich Mendeleyev developed the periodic table of the elements, in which the known elements were organized into groups with similar chemical properties. There were blank spaces in the table, in which he predicted that some yet undiscovered elements would be located. In 1869, he predicted that an element with an atomic mass between 40 and 48 should be located in one blank space, which he called ekaboron. In 1879, Lars Fredrick Nilson discovered a new element from the minerals gadolinite and euxenite using spectral analysis. This element fitted into the blank space in the periodic table for ekaboron. Nilson called the element scandium because it was found in Scandinavia. He produced 2 grams of scandium oxide.

Because of the rarity of scandium and the difficulty of separating it from its minerals, scandium metal was not produced until 1937. Electrolysis was used to prepare a small amount of scandium. The first kilogram of scandium was not produced until 1960. Then the properties of the metal could begin to be studied. Small amounts of scandium were added to aluminum, and the alloy was used in the aerospace industry, first in the Soviet Union and then in the United States. Most companies today use scandium oxide rather than the metal because the former costs only several thousand dollars per kilogram, whereas the latter costs a few hundred thousands of dollars per kilogram.

Obtaining Scandium

Scandium is obtained as a by-product from the processing of other elements from surface deposits or mine tailings. Minerals that are most concentrated in scandium may be physically separated from other minerals in a rock so that scandium oxide may be separated chemically from these minerals.

The amount of scandium oxide produced in the world each year is about 400 kilograms. Russia has stockpiled lots of scandium oxide, so that about 1,600 kilograms of scandium is added to the world supply from this source. Russia originally obtained this scandium from uranium mine tailings. Only about 10 kilograms of metallic scandium are produced each year.

Uses of Scandium

Scandium has been alloyed with aluminum and other metals in the amount of 0.1 to 0.5 percent to maintain low density and strength in the metal alloys. Russia was the first country to use scandium and aluminum alloys in the military, and they were used in MiG fighter planes and in nose cones of submarine-launched missiles. The missiles could be launched below the Arctic ice, piercing the ice without being damaged.

Scandium has more recently been alloyed with aluminum for uses in sports and camping equipment, such as in baseball bats, golf clubs, lacrosse sticks, bicycle frames, and tent poles. For instance, the National Collegiate Athletic Association allowed aluminum bats to be used in college baseball games starting in 1974. One study found that teams’ batting averages increased by twenty points and the number of home runs doubled, so most batters wanted to use aluminum bats. Thus, few wooden bats have been sold since this time because of these dramatic results. Major League Baseball teams, however, must still use wooden bats. Aluminum bicycle frames with added scandium have a 50 percent increase in strength, a 24 percent reduction in fatigue, and 12 percent less weight than aluminum frames without scandium.

Also, the gun maker Smith and Wesson makes what it calls an AirLite handgun, in which scandium is alloyed with the metal. This makes the revolver fairly light in weight and stronger than other guns.

Some mercury vapor lamps have scandium iodide added to them to give a light that has the color spectrum of sunlight. This is useful for scenes in movies and television; it gives the appearance of being outside even though the scene is shot indoors. Also, a radioactive isotope of scandium has been added to petroleum in oil refineries as a tracer. In addition, the strength of aluminum welds between aluminum parts is much stronger if scandium is added to the aluminum weld. Finally, scandium has been alloyed with the elements erbium, chromium, yttrium, and gallium in a garnet laser used in the dental industry. Such lasers remove debris from the teeth and kill bacteria.

There are other potential uses of scandium. Scandium alloys could have uses in cars and airplanes to reduce weight, to increase strength within moving parts, and to reduce corrosion of the parts. The main problem in using scandium is its high cost. Often, using other metal alloys like titanium is more economical, because they are cheaper but have properties somewhat similar to those of scandium.

Bibliography

Ahmad, Zaki. “The Properties and Application of Scandium-Reinforced Aluminum.” Journal of the Minerals, Metals, and Materials Society 55, no. 2 (2003): 35-39.

Bjerklie, Steve. “A Batty Business: Anodized Metal Bats Have Revolutionized Baseball but Are Finishers Losing the Sweet Spot?” Metal Finishing 104, no. 4 (April, 2006): 61-62.

Simpson, Robert S. Lighting Control-Technology and Applications. Boston: Focal Press, 2003.

Zakharov, V. V. “Effect of Scandium on the Structure and Properties of Aluminum Alloys.” Metal Science and Heat Treatment 45, nos. 7-8 (2003): 246-253.

WebElements. Scandium: The Essentials. http://www.webelements.com/scandium/