According to Southern Jewelry News, "The Star of Bombay sapphire belongs to the mineral species corundum.

Pure corundum is colorless, but trace amounts of transition elements like vanadium or chromium result in different colors in the crystal.

[1] The gem was first acquired by Trabert & Hoeffer Inc. of Park Avenue in New York City and was set in a platinum ring.

Edward Stotsenberg of the Mary Pickford Foundation called the Smithsonian and a representative was sent out to examine the stone.

According to Stotsenberg, the representative stated that the Star of Bombay was much brighter than other stones and pried it from the clasps and returned to the Smithsonian with it.