Clean Tech, Virtual Wall Street: About Zirconium

History

Zirconium is the metal found in several related gems: zircons, jacinths, hyacinths, and jargoons. These are all forms of zirconium silicate in various colors. The gemstones were widespread and well known in ancient times. Early chemists examined the stones, but overlooked the presence of a new metal. Then, the German chemist Martin Heinrich Klaproth in 1789 isolated an oxide from a jargoon. He called this substance zirconia and stated that it contained a new element.

Within a few years, other chemists confirmed Klaproth's work. Humphry Davy attempted to extract the metal from zirconia by means of electrolysis, but he failed. Finally, Jons Jakob Berzelius succeeded in 1824. He used potassium to wrest the oxygen from the metal, now called zirconium.

Mining and Production

Zircon is the primary source of zirconium. It occurs by itself but is more commonly separated from the titanium minerals, ilmenite and rutile. About 1.4 million tonnes of zircon were mined in 2014, with Australia being the largest producer (42%). Some zircon is gem quality; almost all is left as zircon or converted to zirconia, with only a small amount being reduced to the metal.

Zirconium the metal can be obtained from zircon with effort using the Kroll process. This is the same process used to produce titanium, which is chemically similar. The chloride of zirconium is heated with either magnesium or sodium to isolate the pure metal.

Properties and Uses

Zirconium is grey, soft, lustrous, and malleable. It is chemically similar to titanium and hafnium. All three are found together in nature, with titanium being the most abundant and hafnium being by far the least.

Zircon gemstones come in many colors with various names, including jacinth (red), hyacinth (yellow), and jargoon (clear, green, or other colors). Zircons should not be confused with cubic zirconias, which are synthetic gems actually made of zirconia.

Metallic zirconium has few uses, but it has a high melting point and resists corrosion. For this reason, zirconium is used in medical instruments and other items that must resist reacting to their environment. Zirconium can also be used to encase nuclear fuel rods because it is quite transparent to neutrons. In this application, it must be very pure.

Zirconia, the oxide, is a chemically inert thermal insulator that withstands high temperatures. It is an excellent coating in ceramics, in jet engines, and in other extreme situations. Zirconia is also very hard and can be formed into ceramic knives.

Zirconium has scattered uses in medicine. For example, zirconium is an active ingredient in dialysis machines. It has no dietary use and is not particularly toxic.