Treatments
September 20, 2022 2023-02-24 1:14Treatments
Sapphire Treatments
Hart & Halo only offer completely natural untreated sapphires,
or those which have been standard heat-treated, and it will always be disclosed.
(Heat treatment is essentially the same as what Mother Earth does to them under the Earth’s crust).
Standard heat
Sapphires are often heat-treated to remove silk inclusions and enhance their clarity and colour. It is said that only around 1-5% of the world’s sapphires are left untreated. Standard heat treatment is an accepted practice within the industry which helps to improve the sapphire’s appearance. The feeling is that heat treatment mimics what happens within the Earth’s crust anyway and being that there is no addition of elements or chemically changing the structure in any way. Heat treatment is permanent and stable.
Beryllium or Titanium diffusion
This is where the sapphire is heated to near melting point in the presence of either Beryllium or Titanium which diffuses into the stone and enhances or changes its colour. In the case of Titanium diffusion, which is used to deepen the colour of a pale blue stone, the penetration is only surface level so nicks, chips or re-cutting can reveal the original weak colour. Beryllium diffusion is a newer technique which is able to penetrate deeper into the sapphire and is often used to invoke orange or golden hues.
Irradiation
Some sapphires are exposed to controlled radiation in order to create a more desirable colour. While these stones are safe to wear, in some cases the colour is not stable and will fade if exposed to bright light or heat. Irradiation is routinely used to colour some diamonds, beryls, and most commonly, topaz.
Fracture filling / Flux healing
At any point when a crystal grows it may fracture, sometimes this heals naturally and leaves an inclusion which we’d refer to as a fingerprint or feather. If this doesn’t heal naturally, the sapphire may be treated at high temperatures with a flux which actually dissolves the surfaces, including the internal surfaces of cracks. When cooled the molten flux may either solidify into a glassy mass (fracture filling) or facilitate the molten corundum re-crystallizing within the cracks, filling and ‘healing’ the fractures shut (flux healing).
What is a flux? Simply a material that is usually solid at room temperature that melts when heated and is used to dissolve minerals.
