gems, garnet, andradite, demantoid, Eritrea

Characterizes demantoid garnets recovered from sandy gravels near Asmara, Eritrea. Examination of eight faceted stones and a parcel of rough totaling nearly 240 ct identified some specimens as peridot; the remainder were demantoid, with specific gravities of 3.80–3.88 and refractive indices exceeding a standard refractometer’s range. Absorption spectra show features associated with ferric iron and chromium. Horsetail inclusions resembling those in Russian demantoid were observed. The association with peridot suggests an origin in serpentinized peridotite.