Corundum
Ruby
Mozambique
3.59 carats
© Palagems
Corundum is called Ruby if red and Padparadscha if pink-orange. All other colours are called Sapphire.
High-quality ruby and sapphire have always been among the most expensive gems and are used in the most prestigious adornments.
Corundum Gemstones by Colour
This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
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Corundum Gemstones by Size
This table shows distribution of Corundum gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.09 cts
Heaviest:563.35 cts
Average:5.63 cts
Total photos:394
Do you have a larger Corundum? Why not upload a photo?
Significant stones
Eminent Star6,465 cts
Ecce Homo Star Ruby2,890 cts
| General Information | ||||||||||||||||||||||||||||||||||||||||||||||
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| Varieties/Types: | Ruby - A red gem variety of corundum Flux-Grown Ruby - A synthetic ruby grown from alumina dissolved in a molten flux. Geneva Ruby - Earliest synthetic rubies (circa 1885) created in Geneva. Star Ruby - A chatoyant ruby showing asterism. Verneuil Ruby - A synthetic ruby created using the flame fusion process. Padparadscha - A salmon-pink coloured Sapphire. Star Sapphire - A chatoyant sapphire showing asterism. | |||||||||||||||||||||||||||||||||||||||||||||
| Chemical Formula |
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| Significant stones | ||||||||||||||||||||||||||||||||||||||||||||||
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| Corundum Treatments | ||||||||||||||||||||||||||||||||||||||||||||||
| A significant percentage of the corundum gemstones are enhanced. Artificial healing of cracks and cavities and high-temperature thermal processing are used to increase the transparency and to improve the colour (Nassau, 1981). Near surface cracks are healed with wax or with silicate glass, during which the processable stone is immersed into a silicate melt or heated in conjuction with a powder-like filling material such as, borax or glass. At high-temperatures the filling material melts and enters into cracks and cavities (Themelis, 1986). | ||||||||||||||||||||||||||||||||||||||||||||||
| Physical Properties of Corundum | ||||||||||||||||||||||||||||||||||||||||||||||
| Mohs Hardness | 9, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Specific Gravity | 3.90 to 4.05, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Cleavage Quality | None, Geology of gems (2003) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Fracture | Uneven,Conchoidal, Geology of gems (2003) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Optical Properties of Corundum | ||||||||||||||||||||||||||||||||||||||||||||||
| Refractive Index | 1.758 to 1.780, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Optical Character | Uniaxial/-, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Birefringence | 0.007 to 0.010, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Pleochroism | Dichroism: blue - violet-blue and greenish-blue; green - yellowish-green; yellow - pale yellow; purple - violet; orange, yellowish-red - deep crimson., Geology of gems (2003) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Dispersion | 0.018, Gemstones (2009) | |||||||||||||||||||||||||||||||||||||||||||||
| Colour | ||||||||||||||||||||||||||||||||||||||||||||||
| Colour (General) | All colours, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Causes of Colour | Purple, Fe2+-O-Ti4+ charge transfer coexisting with Cr3+ in octahedral coordination. Blue, Fe2+-O-Ti4+ charge transfer with influence of Fe2+→Fe3+ charge transfer. Green, Fe3+ in octahedral coordination coexisting with Fe2+→Ti4+ charge transfer, Ti3+ and Cr3+ in octahedral coordination. Yellow, O2-→Fe3+ charge transfer; Fe3+ and Ti3+, a variety of unstable color centers of unknown structure; Fe3+ pairs. Orange to orange-brown Cr3+ in octahedral coordination and color centers; with a contribution of Fe3+. Orangy pink ("padparadscha"), Cr3+ in octahedral coordination and color centers, Cr4+ in octahedral coordination due to Cr4+ and Mg2+ substituting for Al3+ in the crystal structure. Red (ruby), Cr3+ in octahedral coordination with minor contributions of V3+ and Fe3+ in octahedral coordination. Pink, Cr3+ in octahedral coordination. Color-change, Cr3+ and/or V3+ in octahedral coordination in a particular range of concentration, Pragmatic Spectroscopy For Gemologists (2011) | |||||||||||||||||||||||||||||||||||||||||||||
| Transparency | Transparent,Translucent,Opaque, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Lustre | Adamantine,Vitreous, Gemstones (2009) | |||||||||||||||||||||||||||||||||||||||||||||
| Crystallography of Corundum | ||||||||||||||||||||||||||||||||||||||||||||||
| Crystal System | Trigonal, Gemmological Tables (2004) More from other references | |||||||||||||||||||||||||||||||||||||||||||||
| Habit | Tabular, barrel-shaped, Gemstones (2009) | |||||||||||||||||||||||||||||||||||||||||||||
| Geological Environment | ||||||||||||||||||||||||||||||||||||||||||||||
| Where found: | Found in granular limestone, gneiss, mica or chlorite schists., Gemstones (2009) | |||||||||||||||||||||||||||||||||||||||||||||
| Spectrographic Data | ||||||||||||||||||||||||||||||||||||||||||||||
| Calculated Spectra: Click spectra for more information | Ruby - Locality: Hunza, Pakistan Ruby - Locality: Winza, Tanzania Ruby - Locality: Winza, Tanzania Sapphire - Locality: Unknown Sapphire - Locality: Afghanistan Sapphire - Locality: Kenya Sapphire - Locality: Mozambique Sapphire - Locality: Tunduru, Tanzania Sapphire - Locality: Unknown (possibly Australia) Sapphire - Locality: Unknown Verneuil Ruby - Locality: Synthetic Verneuil Ruby - Locality: Synthetic | |||||||||||||||||||||||||||||||||||||||||||||
| Inclusions: rutile, zircon, apatite, calcite, spinel, etc., healing cracks, liquid and two-phase inclusions, negative crystals, hollow tubes (boehmite tubes), twinning lamellaes - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 26 | ||||||||||||||||||||||||||||||||||||||||||||||
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