Greek, Etruscan and Roman garnets in the antiquities collection of the J. Paul Getty Museum

摘要

The results of quantitative electron microprobe analyses and observations of gemmological properties and microscopic features are presented for 11 garnets of ancient Greek, Etruscan and Rdman manufacture. In addition to chemical data, the gemmological properties of the Getty Museum garnets are presented, including refractive index, density and inclusions. According to their chemical composition and gemmological properties, the 11 garnets were subdivided into four groups: Cr-poor pyrope, Mn-rich almandine, Ca-rich aimandine and intermediate pyrope-almandine. Combining the data of the 11 Getty garnets with published analyses of 26 Greek and Roman garnets from ancient jewellery and glyptic, the chemical distribution pattern of all 37 garnets expanded the boundaries of the established four groups and added a fifth garnet group comprising Mn-poor almandine. The compositional fields for these five groups are compared with data reported for Early Medieval garnets, mostly from Merovingian cloisonne jewellery. The chemical composition and physical properties of the garnets yield insights into possible sources of rough gem material, networks of trade/transmission in the ancient world, and associations between finished objects now dispersed in different collections.