Certified origin. Untreated material. Average brilliancy of 40 to 60%. Add to 20% or deduct to 10% for other cutting. Prices for ovals and cushions. Add 8% to 10% for rounds and pears. Add 10% to 20% for emeralds and marquis.
Heat treated material. Average brilliancy of 40% to 60%. Add to 20% or deduct to 10% for other cutting. Prices for ovals and cushions. Add 8% to 10% for rounds and pears. Add 10% to 20% for emeralds and marquis. Note: If certified Burmese and untreated, add 50%, except fair or lower grades. Typically, mid-quality untreated blue sapphire will sell for 20-30% more than a treated stone of the same quality. Top-quality unheated stones could get a premium of 50% or higher, especially if they’re large.
Average brilliancy of 30% to 40%. Add to 20% or deduct to 10% for other cutting. Prices for ovals and cushions. Add 7% to 10% for rounds, pears and marquis. Add 15% to 30% for emerald cuts.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Name||Color Change Sapphire|
|Is a Variety of||Sapphire|
|Colors||Usually, blue, bluish purple, and violet-purple. More rarely, green, yellow, and pink.|
|Fracture||Conchoidal; frequent parting|
|Crystallography||Hexagonal (trigonal). Crystals common, often barrel-shaped, prisms with flat ends, sometimes bipyramidal; also massive, granular, in rolled pebbles.|
|Luminescence||Natural color change sapphires: inert to strong red in LW, inert to moderate red to orange in SW. Synthetic color change sapphires: moderate orange to red in LW and SW, may fluoresce red in LW and mottled blue in SW.|
|Luminescence Type||Fluorescent, UV-Long, UV-Short, X-ray Colors|
|Absorption Spectrum||The ferric iron spectrum dominates these stones. In green and blue-green gems, rich in iron, there are lines at 4710, 4600, and 4500 in the blue-green region. Also lines at 4500 and 4600 may seem to merge and become a broad band. The three bands described are generally known as the 4500 complex and are very distinctive in sapphires. Some blue Sri Lanka sapphires also show a 6935 red fluorescent line, and the 4500 line is very weak in these gems. Synthetic color change sapphires show a line 4740. See main Sapphire gem listing for more information.|
|Pleochroism||Very pronounced. See main Sapphire gem listing.|
|Optics||RI: o = 1.757-1.770; e = 1.765-1.779 (usually 1.760, 1.768); Uniaxial (-).|
|Optic Sign||Uniaxial -|
|Luster||Vitreous to adamantine.|
|Polish Luster||Vitreous to subadamantine.|
|Specific Gravity||3.99-4.10; usually near 4.0.|
|Transparency||Transparent to opaque.|
|Phenomena||Asterism, color change, chatoyancy.|
Color change sapphires are those that change color between light sources.