Abstract
A silver Torah shield fitted with a set of precious stones and glass imitations crafted in Poland in the first half of the 19th century was investigated using two of the currently distributed portable and relatively low-cost Raman spectrometers in situ at the Jewish Museum in Prague. Observed Raman peaks corresponded well (+/- 3cm(-1)) to the reference values.
The hand-held instruments operated at 785- and 532-nm laser excitations showed good performance in the fast and unambiguous identification of nearly 60 stones which were fitted on the shield: one blue aquamarine, three purple amethysts, thirteen red garnets (all classified as high-percentage almandines), three white pearls, fifteen pieces of red coral and five chalcedonies (one white and four red). All of the other stones were identified as colored glass.
The rather chaotic mixture of stones of various colors, cuts and sizes and the total volume of imitation glass support the theory that the mounted stones were gathered from Jewish households and donated for the adornment of the shield. The common portable Raman instruments represent an ideal tool for the quick and accurate identification of gemstones mounted in historical artifacts in situ in the framework of museum or collection sites in a non-destructive way.