Tagarchief: Saffier

‘pigeon blood red’ and ‘royal blue’ standards

Switzerland’s SSEF and Gübelin Gem Lab agree to harmonise ‘pigeon blood red’ and ‘royal blue’ standards

The Swiss-based Gübelin Gem Lab and Swiss Gemmological Institute SSEF, recognised as the leading laboratories for coloured stone testing, have agreed to harmonise their standards for the colour terms “pigeon blood red” and “royal blue.” Their goal is to standardise the usage of these terms for the benefit of the international gemstone trade.

Download the press release (pdf)

Diffuus behandeling

Om een bleke steen kleur te geven kan deze een diffuus behandeling krijgen.

Bij saffier werd dit vroeger veel gedaan met titanium maar gebeurt tegenwoordig vaker met beryllium. Omdat beryllium een kleinere atoom structuur heeft.

Hiervoor wordt de steen verwarmt tot net onder het smeltpunt in de aanwezigheid van het element dat de kleur moet veroorzaken. Hierdoor zal in de buitenste laag van de edelsteen het element worden opgenomen in het kristalrooster.

Als de steen beschadigd of verslepen wordt dan kan de oorspronkelijke kleur weer naar voren komen omdat deze behandeling alleen in de buitenste laag van de edelsteen zit.

Meer uitleg vind u op GIA onder ‘Lattice diffusion’

Cobalt-Colored Composite Sapphires Now Entering the Market

Composite Sapphires.jpg

28 January 2013: NEW YORK – American Gemological Laboratories (AGL): Gemstone treatments are a regular issue which the gemstone trade has to contend with. In May 2012, AGL first learned of a new type of treated sapphire which was becoming available in the Bangkok market “This treatment was first described to me as a new type of lead-glass treated corundum where a blue colorant was also introduced.” indicated Christopher P. Smith, President of AGL.

In November and December of 2012, clients of the AGL contacted the lab indicating that such stones were starting to be encountered in the marketplace. Recently a couple of samples were sent to the AGL by Dr. Cigdem Lule of GemWorld International Inc. Although the stones appeared fairly transparent and had a convincing “blue sapphire” color, color concentrations were readily visible upon closer scrutiny even with the unaided eye and were obvious with magnification using a 10x loupe or microscope (figure 1 below).

“A chemical analysis readily showed a high concentration of lead in addition to the aluminum oxide of corundum, with trace elements of iron and gallium, while a visible spectrum revealed absorption bands associated with cobalt.” Smith stated (figure 2 below).

To read the full press release please download the PDF by clicking here

Composite Sapphire Sample Report

Source: AGL