Sapphires from the Andranondambo Region, Madagascar

Sapphires from Antsiranana Province, Northern Madagascar

“…The UV-Vis-NIR absorption spectra of the Ambondromifehy BGY magmatic sapphires have features typical of those seen in basaltic sapphires from other localities (Schmetzer, 1987;Schmetzer and Kiefert, 1990;Kiefert and Schmetzer, 1991;Krzemnicki et al, 1996;Schwarz et al, 1996;Sutherland et al, 1998b). Therefore, absorption spectra cannot be used to distinguish Ambondromifehy sapphires from those of other basaltic fields.…”

“…The gemological characteristics of sapphires from Andranondambo, southeastern Madagascar, were detailed by Schwarz et al (1996) and by Kiefert et al (1996). Subsequent studies of the associated mineral assemblages attributed their formation to metamorphic skarn processes (Gübelin and Peretti, 1997).…”

“…These analyses were performed with a Tracor Northern Spectrace 5000 system, using a program specifically developed for trace-element geochemistry of corundum by Prof. W. B. Stern, Institute of Mineralogy and Petrography, University of Basel. These data were compared to EDXRF results of Schwarz et al (1996) for sapphires from Andranondambo, Madagascar.…”

“…In the blue and greenish blue sapphires, the basic absorption spectrum found in yellow sapphires was superimposed by intense absorption bands assigned to Fe 2+ /Ti 4+ charge transfer (maximum at about 560 nm with polarization ^c > ||c), as well as to an Fe 2+ /Fe 3+ pair absorption (maximum at about 870-880 nm with polarization ^c > ||c; figure 24B and C)*. Due to the high intensity of *Because of technical inconsistencies, the polarized absorption spectra of magmatic sapphires published by Schwarz et al (1996) and Sutherland et al (1998b) /Ti 4+ maximum at about 700 nm with polarization ||c ² ^c (see figure 24E) is generally not resolvable. The spectra of the heat-treated intense blue-violet samples were identical to those of untreated sapphires of similar color.…”

“…island, approximately 90 km northeast of Tolanaro/Fort Dauphin (Schwarz et al, 1996;Kiefert et al, 1996;Milisenda and Henn, 1996;Gübelin and Peretti, 1997;figure 2, inset). During the years following the Andranondambo "rush," other deposits were discovered in the same region.…”