Garnets from Madagascar with a Color Change of Blue-Green to Purple

Pink to Pinkish Orange Malaya Garnets from Bekily, Madagascar

“…An iron band at this wavelength is commonly observed in iron-bearing rhodolites without significant manganese, vanadium, or chromium, but this band also has been attributed to V 3+ and/or Cr 3+ in garnets (Amthauer, 1976;Schmetzer and Ottemann, 1979;Schmetzer et al, 1980;Schmetzer and Bernhardt, 1999). Small amounts of V 2 O 3 and Cr 2 O 3 were recorded in our samples (table 1), so the absorption at 569 nm is partially due to these trace elements.…”

“…As noted above, garnets with a color change from blue-green to purple are mined in the vicinity of the malaya garnets described here (Schmetzer and Bernhardt, 1999 garnets are members of the pyrope-spessartine series, with similar features. The only significant differences are the distinctly higher vanadium (about 1 wt.% V 2 O 3 ) and chromium (about 0.20 wt.% Cr 2 O 3 ) contents in the color-change garnets.…”

Diffusion of chromium in chrysoberyl

“…The color change between green (daylight, ''D65''), having a correlated color temperature of approximately 6500 K, and red (incandescent light, ''A'') [5][6], which has a correlated color temperature of about 2856 K, is highly valued in the gem trade. This color change is what is called the ''Alexandrite effect'' [7], which is observed in gemstones including alexandrite, alexandrite-like sapphire [8], alexandrite-like spinel [9], and alexandritelike garnet [10]. This color change effect is due to the presence of chromium as prominent impurity.…”

New gemstone occurrences in the south-west of Madagascar

“…In the first detailed gemmological study of colour-change garnets from Madagascar, Schmetzer and Bernhardt (1999) separate colour-change garnets into two groups according to their chemistry. Most colourchange garnets are intermediate members of the pyrope-spessartine solid solution series containing minor amounts of vanadium a n d / o r chromium (Jobbins et al, 1975;Stockton, 1982;Manson and Stockton, 1984;Stockton and Manson, 1985;Koivula and Kammerling, 1988;Johnson and Koivula, 1996b;Johnson and Koivula, 1998b;Schmetzer and Bernhardt, 1999). All studied colour-change garnets from Madagascar belong to this group (Johnson and Koivula, 1998b;Schmetzer and Bernhardt, 1999).…”

“…Most colourchange garnets are intermediate members of the pyrope-spessartine solid solution series containing minor amounts of vanadium a n d / o r chromium (Jobbins et al, 1975;Stockton, 1982;Manson and Stockton, 1984;Stockton and Manson, 1985;Koivula and Kammerling, 1988;Johnson and Koivula, 1996b;Johnson and Koivula, 1998b;Schmetzer and Bernhardt, 1999). All studied colour-change garnets from Madagascar belong to this group (Johnson and Koivula, 1998b;Schmetzer and Bernhardt, 1999). Only a few colour-change garnets were found to be chromium-rich (Schmetzer et al, 1980).…”