166 Mineralogical Characterization of Economic Resources: From Critical Minerals to Gemstones

From ore materials to precious gemstones, minerals play an important role in almost every aspect of our lives. This session will focus on characterization of economic minerals employing spectroscopic techniques, geochemical analysis, and microanalytical techniques.

Tuesday, 21 October 2025
8:00 AM - 12:00 PM
HBGCC, 217A

Studying and Exhibiting the Winston Red Diamond at the Smithsonian NMNH

Paper number: 166-9
Program: Technical Sessions
Time: 10:10 AM – 10:30 AM

Authors

Abstract

The Winston Red diamond is the latest major addition to the National Gem Collection at the Smithsonian Institution’s National Museum of Natural History (NMNH). This study is the first to examine the science and history behind this storied and extremely rare jewel. At 2.33 cts, it is currently the fifth-largest known Fancy red diamond in the world, based on all of the Fancy red diamonds examined by GIA (n= 399). The team from Smithsonian, GIA, and the Paris School of Mines applied optical, spectroscopic, cathodoluminescence, UV, and photoluminescence approaches to determine the source of its color and geographic origin. FTIR reveals that the Winston Red is a type IaAB (A) Group 1 “pink” diamond and that the crimson color is due the strong 550 nm band associated with plastic deformation, coupled with nitrogen-related N3 (N3V0), H3 (N2V0), and H4 (N4V20) defects. Plastic deformation bands and dislocation network “fish scale” patterns revealed by CL, PL, and optical microscopy suggest that this red diamond developed its color through high pressure and temperature conditions. With the added help of historical references involving Cartier and a Maharaja, these mineralogical characteristics allow us to narrow down the likely crater age and geographic origin of the stone to either Brazil or Venezuela. The Winston Red diamond was unveiled on April 1st, 2025 and is currently on public exhibition in the Winston Gallery of the NMNH, next to the Hope Diamond.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413338

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