New data are presented for demantoid from Val Malenco, Italy, as obtained by classical gemological methods, electron microprobe and LA-ICP-MS chemical analyses, and UV-Vis-NIR and mid-IR spectroscopy. The results confirmed that these garnets are almost pure andradite (≥98 mol%, RI >1.81, SG = 3.81–3.88). All 18 samples studied contained “horsetail” inclusions, which are characteristic of a serpentinite geologic origin. Fe and Cr control the coloration of demantoid, though color variations in these samples were mainly correlated to Cr content.
Demantoid from Val Malenco, Italy: Review and Update / I. Adamo, R. Bocchio, V. Diella, A. Pavese, P. Vignola, L. Prosperi, V. Palanza. - In: GEMS & GEMOLOGY. - ISSN 0016-626X. - 45:4(2009), pp. 280-287.
Demantoid from Val Malenco, Italy: Review and Update
I. AdamoPrimo
;R. BocchioSecondo
;A. Pavese;
2009
Abstract
New data are presented for demantoid from Val Malenco, Italy, as obtained by classical gemological methods, electron microprobe and LA-ICP-MS chemical analyses, and UV-Vis-NIR and mid-IR spectroscopy. The results confirmed that these garnets are almost pure andradite (≥98 mol%, RI >1.81, SG = 3.81–3.88). All 18 samples studied contained “horsetail” inclusions, which are characteristic of a serpentinite geologic origin. Fe and Cr control the coloration of demantoid, though color variations in these samples were mainly correlated to Cr content.
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