A historical alexandrite at Paris School of Mines

Abstract

International audienceKept in the vault since its donation to the museum in 1882, a 42.54 ct alexandrite (Fig. 1) will finally be revealed in 2023 during a temporary exhibition at the Mineralogy Museum of Mines Paris - PSL (Paris School of Mines), France. The reasons why this exceptional stone was never exhibited are not well constrained, but we can hypothesize that 1- the value of the gem was too high and as a safety precaution it was kept in the vault, 2- it was too difficult to properly exhibit the stone to show its change-of-color, 3- at the time of its arrival, gems were not of interest to the curatorial staff (M. Ernest Mallard).The opportunity to show off this rare collector’s stone is eventually found: a temporary exhibit is under development and will highlight important historical stones, including this hidden treasure. The exhibit untitled “Minerals - Objects of Collection”, meant to open mid-2023, will display the different ways through which the museum’s collection grew: donations, purchases, exchanges, custodies, confiscations and field trips. The alexandrite will be presented in its own showcase as a “secret revealed” from the collection, in the donations theme.Before being exhibited, the alexandrite is undergoing a research project: its history is being investigated and its gemological properties characterized. This investigation is part of an ongoing project on the study of historic gems of the Mineralogy Museum of Mines Paris - PSL, in partnership with the French Gemological Laboratory (LFG). The classical gem characterization was conducted at the museum while the microscopic, chemical and spectroscopic analyses at the LFG in Paris, respecting time constraint due to security reasons. In this lecture, we will present its journey before arriving at the museum, from the gem cutter that faceted it, exhibited it at the World Fair in Paris in 1878, and eventually donated it to the museum fou