Nano inclusions in sapphire samples from Sri Lanka
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The turbid/translucent, near colorless (milky) metamorphic sapphire samples from Sri Lanka have been characterized after the heat treatment in N2 at 1650 oC. As-received sapphire specimens became bluish-colored and exhibited more clarity after the heat treatment. It was found that the color change at inclusions zoning region is attributed by the dissolution. As received samples contain the micro/nano inclusions such as rutile (TiO2), ilmenite (FeTiO3), spinel (MgAl2O4)/ulvospinel (Fe2TiO4) and apatite (Ca5(PO4)3), which were dissolved by the heat treatment and form the blue color through Fe2+/Ti4+ charge transferring. The microstructures become different because as the dissolution of apatite (Ca5(PO4)3(OH,F,Cl)) in alumino silicates (Al2SiO5) occurred, resulting in morphological change with the appearance of (Ca, Mg, Al) silicate on the surface. Both as-received and heat treated samples showed the rhombohedral crystal structure of Al2O3.
Abstract
The turbid/translucent, near colorless (milky) metamorphic sapphire samples from Sri Lanka have been characterized after the heat treatment in N2 at 1650 oC. As-received sapphire specimens became bluish-colored and exhibited more clarity after the heat treatment. It was found that the color change at inclusions zoning region is attributed by the dissolution. As received samples contain the micro/nano inclusions such as rutile (TiO2), ilmenite (FeTiO3), spinel (MgAl2O4)/ulvospinel (Fe2TiO4) and apatite (Ca5(PO4)3), which were dissolved by the heat treatment and form the blue color through Fe2+/Ti4+ charge transferring. The microstructures become different because as the dissolution of apatite (Ca5(PO4)3(OH,F,Cl)) in alumino silicates (Al2SiO5) occurred, resulting in morphological change with the appearance of (Ca, Mg, Al) silicate on the surface. Both as-received and heat treated samples showed the rhombohedral crystal structure of Al2O3.
참고문헌 (7)
- P. Wathanakul, "Nano-inclusions and coloration in blue sapphire from Sri Lanka and Madagascar", 1 st International Gem and Jewelry Conference (2006)
- H. Kitawaki, "Identification of heated corundum", Gemmological Society of Japan Conference (2005)
- Identification of heated, "unheated status on ruby and sapphire", GAAJ, 2007
- S. Tipprasert, "Thermal enhancement and characteristics of sapphires from Wellawaya, Sri Lanka", 석사, pp.2006
- V.N. Makarov, "Solubility of apatite in aluminosilicate melts of the albite-diopside, anorthite-diopside, and orthoclase-diopside systems", Glass Physics and Chemistry, 28(3), pp.177~ (2002)
- C.S. Hurlbut, JR., "Dana’s Manual of Mineralogy. 18 th ed", pp.579~ (1971), John Wiley & Sons
- E. Savrun, "The effect of titanium doping on the high-temperature rhombohedral twinning of sapphire", J.Mat. Sci., 36, pp.2295~ (2001)