Artificial garnets that come in a much wider range of colors than their naturally formed counterparts have been synthesized by Russian researchers. The crystals, which are composed of yttrium and alumina, with specific metal additives, seem the same as natural garnets but are harder and can be fine tuned to be almost any color rather than being limited to red. The initial application will be in novel jewelry.

Jewelers would love to get their hands on blue garnets (Credit: David Bradley)

L.I. Kazakova, G.M. Kuzmicheva, and E.M. Suchkova of the All-Russian Research Institute of Raw Materials Synthesis at Aleksandrov, Moscow State, have improved the synthetic procedure for making garnets. Their technique does not sacrifice quality for speed so they can quickly make synthetic stones that are just as good, if not better, than the real thing! The new materials have a uniformity of color distribution as well as being harder than natural garnets.

Yttrium-aluminum garnets without additives are colorless, but a few atoms of a rare earth metal is enough to give them almost any hue desired. To make yttrium-aluminum crystals with the structure of garnet, aluminum oxide and yttrium oxide were melted in a ratio of 3:5; on crystallization, the resulting mixture was ground into 5 mm granules. Calcined powders of hafnium or titanium were mixed with the granules and the mixture melted in a vacuum and cooled by pulling the reaction vessel slowly away from the heat source.

Artificial garnets can now be made in a range of colors (Credit: Galina Kuzmicheva)

The researchers produced red and green garnets, as well as a garnet of pale blue, a color not found in natural garnets. The red coloring of yttrium-aluminum garnets is caused by inclusion of zirconium ions in the crystal structure. The researchers say that increasing the amount of zirconium may intensify the color. The researchers found that scandium oxide improved the deepness and evenness of the red color; bright red through to crimson garnets were produced. By replacing yttrium ions with europium, the researchers could make garnets with a violet hue, while ytterbium, zirconium, and cerium produced green garnets. Europium, zirconium, and terbium ions within the crystal structure of yttrium-aluminium garnets gave rise to the unique pale-blue stones.