Learn more about the mineral called allanite – its characteristics, history, and uses and applications.
Allanite is a silicate mineral, which means it appears in a crystal-like form. Its chemical makeup is (Ce,Ca,Y,La)2(Al,Fe+3)3(SiO4)3(OH). It is commonly found in igneous rocks and clay-rich sediments.
Allanite is one of the most common sources of rare earth minerals that are crucial in many industries and technologies. Mineralogists classify allanite as belonging to the epidote group of minerals. As an individual mineral, 20% of an allanite is composed of rare earth metals, particularly cerium, lanthanum, and yttrium. It may also contain other elements in smaller quantities; these minerals include thorium, chromium, barium, phosphorus, uranium, zirconium, and others.
The natural color of allanite falls under the brown to black spectrum, sometimes even brown-violet. It has brown and grey streaks and a vitreous luster which may or may not be coated with a yellow-brown film which geologists believe to be limonite.
Some forms of allanite fall between the spectra of translucent to opaque. When subjected to a temperature as low as 95 degrees Celsius, allanite becomes incandescent – a characteristic of minerals which mineralogists refer to as pyrognomic. It falls under 5.5 to 6 in the Mohs hardness scale, which means it’s brittle to some extent.
Allanite is slightly radioactive and should be handled with utmost care. There should be very limited human exposure to allanite. It exhibits radioactivity due mostly to the radioactive thorium that it contains.
Origin and History
Allanite was first discovered in 1810 by Karl Ludwig Giesecke. He found it in Aluk Island in Greenland. Its name came from Thomas Allan, a Scottish mineralogist who was well-known at the time. Another name for allanite is orthite, a term used in Europe to refer to this kind of mineral.
In terms of distribution, allanite has been found in different countries such as Russia, Sweden, and France in Europe; Madagascar in South Africa; and Canada and the United States in North America.
Uses and Applications
The mineral called allanite is a source of rare earth metals – the essential elements used in a wide array of applications. It can be classified into three groups according to concentration of rare earth mineral that they contain.
Allanite minerals that are rich in cerium are called Allanite-(Ce). This is what most people commonly think of when they say allanite or orthite. The other less common groups of allanite are Allanite-(La), a lanthanum-rich allanite; and Allanite-(Y), an yttrium-rich allanite.
The Allanite-(Ce) is crucial in producing Cerium which is used by industries in the production of polishing powder and chemical oxidizing agent. It is also used in oil refineries, self-cleaning ovens, and glass and ceramics.
The Allanite-(La) produces lanthanum, a rare earth element which is used as an essential ingredient in making high refractive glass, camera lenses, hydrogen storage, battery electrodes, and flint. Like cerium, lanthanum is used by oil refineries as a fluid catalytic cracking catalyst.
The Allanite-(Y), on the other hand, is a rich source of yttrium, another rare earth element. Yttrium is used in making high temperature superconductors. It is also developed into yttrium iron garnet (YIG) microwave filters and yttrium-aluminum garnet (YAG) laser.