Rubies are one of the four rarest gemstones on earth, but we understand little about their geologic formation. Knowing the formation of rubies is important in many ways, as it could increase our ability to find and mine more rubies as well as improve our understanding of their chemical complexities. Furthermore, knowledge of the geological formation of rubies might aid our understanding of major mountain-building episodes. In 2013, RJ Stern and others suggested that rubies, as well as sapphires, form solely in continental collisions; they called them “Plate Tectonic Gemstones”. Additional studies (for example, Beaumont et al., 2007) have shown that rubies form in low pressure, high temperature zones during exhumation of high-pressure and ultrahigh-pressure rocks at the end of a continent–continent collision. To this end, I researched the tectonic history of three locations from which rubies have been mined: the Himalayas, the Appalachians (North Carolina), and Madagascar. For comparison, I investigated the idea that rubies could be formed in other tectonic zones, such as the arc-continent collision of Panama. In addition, I used infrared spectroscopy to identify the crystallography of rubies from the Himalayas, the Appalachians, and Madagascar . My research demonstrates that these rubies were all formed in continent–continent collisions zones, including ultrahigh-pressure collision zones.
Nicole Ahline, ’15
Sponsor: Emily Walsh