✦ These types of rough diamonds, besides being the world's most valuable gemstones based on size and clarity, are remarkable for geological reasons.  Research done at the Gemological Institute of America by Evan Smith and the Carnegie Institution for Science by Steve Shirey, Peng Ni, Anat Shahar, Emma Bullock, and Jianhua Wang shows them to crystallize in the mantle transition zone (440-660 km deep) and to carry metallic inclusions. The iron in the inclusions was derived from magnetite and awaruite crystallized during serpentinization of peridotite on the ocean floor before being carried to great depth by subduction. See: Smith, E.M., Peng, N., Shirey, S.B., Richardson, SH., Wang, W., and Shahar, A. (2021) Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor. Science Advances 7: eabe9773 https://doi.org/10.1126/sciadv.abe9773

Photo above is by Robert Weldon. © 2015 GIA. Courtesy of Gem Diamonds Ltd. This group of type IIa rough diamonds (VRL# 190894) shown here range from 14 to 91 carats and sometimes appear to be broken fragments of once larger diamonds. 

Current Position and Education

A geologist for more than 50 years, Steve Shirey is the senior staff member of the Geochemistry and Cosmochemistry Group at the Earth and Planets Laboratory (EPL). His main interests are in diamonds as the deepest probe of plate tectonics, the igneous evolution of the Earth, and the emergence of Earth's continents. Steve conducts his own research in these areas but equally important is the teaching and training he does of young scientists for their research careers. Steve is currently mentoring 3 postdoctoral fellows; over his career he has advised some 36 additional postdoctoral fellows and 24 PhD students, all of whom have gone on to successful careers as university professors or in industry. Steve is a Fellow of the American Geophysical Union, the Geochemical Society, the Geological Society of America, and the Mineralogical Society of America (MSA). He was 96th President of MSA and the 100th President of the Geological Society of Washington. 

The Earth and Planets Laboratory (EPL) is one of the three divisions that make up the Carnegie Institution for Science —the nation's oldest, privately-endowed, research organization dedicated to fundamental scientific research for the benefit of mankind. The EPL is a recent combination of the former Geophysical Laboratory and the Department of Terrestrial Magnetism. At EPL, research in geophysics, seismology, volcanology, geochemistry, cosmochemistry, astronomy, planetary science, experimental petrology, mineral physics, and material science is carried out on one campus in residential northwest Washington, DC by ~60 resident scientists (25 staff scientists and 35 postdoctoral fellows).  

BA, Geology (1972), Dartmouth College

MS, Geology (1975), University of Massachusetts Amherst

PhD, Geochemistry (1984), Stony Brook University

Postdoctoral Fellowship, Isotope Geochemistry (1984-1985), Carnegie Institution for Science

Scientific Staff Member, Carnegie Institution for Science (1985 to present)