Rosser Reeves Star Ruby

With its rich red color and well-defined star, the 138.72ct Rosser Reeves Star Ruby might be the largest and finest star ruby in the world. Ruby is the gem variety of the mineral corundum. The star forms when titanium atoms are trapped within the growing corundum crystal. As the crystal cools, the titanium forms needlelike crystals of the mineral rutile, which orient themselves in three directions. When properly cut, en cabochon, light reflecting off of the three sets of needles produces the six-rayed star. This phenomenon is called asterism.The Rosser Reeves Star Ruby is from Sri Lanka, but its early history is not known. When it was purchased by a gem dealer in London in the late 1950s, the ruby weighed 140 carats, but it was subsequently recut to center the star. Rosser Reeves, whose name it now bears, carried it around as a lucky stone, referring to it as his baby. He donated it to the Smithsonian in 1965.