corundum, sapphire, Brazil.12, geology.11, gems

About four years ago, Professor J. E. de Souza Campos of the University of São Paulo, Brazil, reported on a new sapphire from Brazil. He mentioned strange inclusions, unknown until now in sapphire and resembling rounded gas bubbles so typical of synthetic corundum. At the author’s request, Professor de Souza Campos very kindly made available two cut stones of this sapphire and later some raw material, which could be tested more easily. The locality of these sapphires is quoted by de Souza Campos as Jauré and Quilombo, Rio Coxim, Mato Grosso. He found the refraction for sodium light to be nₒ = 1.770, nₑ = 1.762, and the birefringence 0.008. The dichroism for blue-coloured stones is o = blue to violet blue, e = green; for greenish-coloured stones o = green, e = yellow-green. With the hydrostatic balance he determined the specific gravity at 3.952 to 4.052. The stones exhibit a dark blue colour but, regrettably, the transparency is considerably reduced by many inclusions. At a first sight through the microscope, many of them indeed resembled rounded gas bubbles. But when using a higher magnification, it is seen that two kinds of inclusions are present: liquid and gas-filled discs, and negative crystals, many of them exhibiting rounded forms.