Gem spinel in the Imperial Crown of the Holy Roman Empire: Evidence for very early gemstone heating?

The Imperial Crown of the Holy Roman Empire, part of the Imperial Regalia, is the key exhibit in Vienna’s Imperial Treasury. It is currently investigated within the three-year interdisciplinary project ‘Crown’ (www.projekt-reichskrone.at) led by Kunsthistorisches Museum Vienna. The research aims, among others, at issues regarding the Imperial Crown’s materials, manufacturing technology and time, as well as its state of preservation. During the first measurement campaign in Spring 2022, we had the task to determine conclusively – and, if possible, to characterise further – all 172 (inorganic) gemstones in the crown, whereas studies of the pearls were planned for the second measurement campaign (2023).