Fig. 7
From: Beautiful Pietàs in South Tyrol (Northern Italy): local or imported works of art?
Mortar sample taken from the Pietà in the Church St. Martin in Göflan: a transmitted light (parallel/crossed Nicols), and Raman microspectroscopic maps of b a cluster of fibrous thermal anhydrite crystals and c grains of thermally stressed primary anhydrite. FWHM denotes the full width at half maximum of the most prominent Raman band of anhydrite II, which enables to differentiate natural from thermal anhydrite and to deduce calcination temperatures, as described in the text and Ref. [52]