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Sapphire Treatments

Sapphire is the variety of Corundum that includes every color except those stones with the dominate color red.  Once the dominate color is red, it is now called a ruby.

Sapphire is aluminum oxide Al2O3 and has the trace element of titanium to produce the blue color.  Other colors have trace elements such as, iron for yellow sapphires, titanium and iron for green sapphires and a combination of chromium, titanium and iron for purple sapphires.  Sapphire has a Mohs hardness of 9 making it very durable for use in jewelry and Steven Kretchmer tension settings.

Oval Swirl

Depending on who you talk to, 90 – 95% of the world’s sapphires are heat treated.  This treatment, in varying degrees, has been done to gemstones for 1000s of years.  Unless otherwise noted via a laboratory report, any type of treatment should be disclosed at time of purchase.  Heat treatment is done to enhance the sapphire’s color and sometimes clarity.  Those stones that have gone through laboratory testing and come out with “no evidence of heat treatment”, can be sold for 1000s of dollars per carat depending on the color, cut, clarity and carat weight of the stone.  Heat treated sapphires can also command high prices per carat but with all values being the same, untreated sapphires would be off the charts.  Untreated sapphires should always be removed from their settings before repairs, standard cleaning is safe.  Heat treated sapphires are stable and will not change with cleaning or standard repairs.

Diffusion treatment is a high heat treatment with titanium, in the case of blue sapphire, to improve the color of light blue sapphires or to change colorless or light yellow sapphires to a more salable blue.  This is often called a surface diffusion treatment since the titanium is just absorbed under the surface of the stone.  This treatment is also used to create asterism (stars) in both natural and synthetic cabochon cut sapphires.  This is a stable treatment and will not change unless the stone has been chipped revealing the lighter color core.

 Diffusion treated sapphire

 Using the element of beryllium in the diffusion treatment can change or enhance every color of sapphire.  The atoms of beryllium are smaller so the absorption often goes completely through the stone making identification of treatment, most of the time, only possible by a laboratory.

Fracture filling has just recently come into play as a sapphire clarity enhancement.  A high lead glass is used to improve the visual clarity of a stone with fractures.  The filler has a similar refractive index as the sapphire and when used in the fractures of the stones, makes them less visible.  This type of treatment is not stable so it is very important to know if your stone has had this treatment before introduced to any heat or cleaning.  This treatment today is mostly seen in ruby but some fracture filled sapphires have surfaced.

fracture filled

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