Researchers Determine Star Material of Idaho State Gem

PULLMAN, Wash. — Researchers from the Washington State University School of Mechanical and Materials Engineering have for the first time determined the cause of the ‘star’ in Idaho’s famous star garnet, the official state gem of the Gem State. Idaho is one of only three places in the world that are known to have star garnets.

While simple curiosity was the initial instigator for the research, the work promises to be of interest, particularly in high technology industries, says Grant Norton, professor in the WSU School of Mechanical and Materials Engineering and associate dean of Research and Graduate Programs for the College of Engineering and Architecture. Crystals with the garnet structure are used in solid-state lasers and are being studied for use in radiation detectors. 

Norton and a colleague first wondered about the stars’ origins after walking into Gem State Jewelers in Moscow, Idaho a few years ago. While there was suspicion of their origin, nobody really knew what caused them.

Using donated garnets from the jewelers, Norton and Maxime Guinel, a graduate student in materials science, used transmission electron microscopy to determine conclusively for the first time that the star is caused by inclusions of rutile, a mineral composed of titanium oxide, in the garnet. The star can either contain six rays or four, based on the orientation of the tiny needles of rutile. They also determined the microstructural characteristics that affect the quality of the ‘star’.

Their results were published today (Feb. 15) in the Journal of Materials Science.