The World's Most Famous Royal Diamond-Koh-I-Noor

According to some sources, the Koh-i-noor diamond was found in the Godavari River in central India 4,000 years ago. The authentic history of this jewel begins in the 14 c. when it was reported to be in the possession of the rajas of Malwa. It later fell into the hands of Baber, who founded the Mogul dynasty in 1526. During the next two centuries the diamond was one of the most prized items in the treasure of the Mogul emperors. Tradition associated with it states that its owner will rule the world, but that to possess it is dangerous for any but a woman.

In 1939, Nadir Shah of Persia invaded India and all of the treasures of the Moguls fell into his hands except the great diamond. Nadir is believed to have exclaimed "Koh-i-noor" mountain of light. Later, Ranjit Singh, the Lion of the Punjab, took the stone and wore it as a decoration.

It was later placed in the Lahore treasury. After the Sikh wars, it was taken by the East India Company as part of the indemnity levied in 1849, and was subsequently presented to Queen Victoria.It was decided to recut it from its original Indian form, and a member of the Amsterdam firm of Costar was called to London to cut the stone and got the oval cut in 108.93 carats. Queen Victoria continued to wear it as a brooch. The actual Koh-i-Noor can now be seen in the Maltese Cross, in a crown made for the Queen Mother in 1937, on display at the Tower of London.

The World's Most Famous Royal Diamond-Cullinan

Cullinan
The Star of Africa, a pear shaped diamond weighing 530.20 carats, aka the Cullinan I. It's called the Cullinan I because it's the largest of the 9 large stones cut from the Cullinan Diamond. The historic Cullinan diamond, found in Premier Mine, South Africa in 1905, weighed an astounding 3,106.75 carats. The Cullinan was cut by Joseph Asscher & Company of Amsterdam, who examined the enormous crystal for around six months before determining how to divide it. The Star of Africa, weight 530.20 carats, holds the place of 2nd largest cut diamond in the world and King Edward placed it in the Sovereign's Royal Scepter. The Cullinan II is a 317.40 carat cushion cut stone mounted in the band of the Imperial State Crown. The Cullinan III is a pear-shaped diamond weighing 94.40 carats, and is the finial of Queen Mary's Crown and can be worn with the IV as a pendant -brooch. The Cullinan IV, a 63.60- carat cushion shape. All are a part of the Crown Jewels, and they are now on display in the tower of London.

Golden Jubilee

The Golden Jubilee is the largest faceted diamond in the world, weighing 545.67 carats in which a yellow-brown cushion shape diamond is now the Crown Jewels of Thailand, The original stone weighted 755.50 carats and then was designed by master cutter Gabi Tolkowsky (He also designed the 278.85 -carat Centenary Diamond, which is the largest D-Flawless diamond in the world.) who took three years to complete its transformation into the world's largest fancy diamond.

The result was that the cutter could preserve the greatest possible amount of the weight of the rough diamond in which he was losing diamond less then 28 percent. Tolkowsky described the Golden Jubilee's cut as a "fire rose cushion cut." The color has been graded as "fancy yellow-brown" by GIA Lab.

The Golden Jubilee is known to have been purchased from De Beers by a Thai syndicate in 1995. The diamond was then given to King Rama IX of Thailand in 1997 for his Golden Jubilee - the 50th anniversary of his coronation. King Rama IX had the Golden Jubilee mounted in his royal scepter. Prior to this event, the stone was simply known as the Unnamed Brown in which was found at the Premier mine, South Africa in 1986.

FRACTURE-FILLED ORANGEY PINK SAPPHIRE WITH LEAD GLASS

In March 2005, GIT-GTL received the orangy pink sapphires for certified; one of which showing the evidences of having undergone the fracture-filled process with lead glass. Our standard gem testing confirmed this stone was natural orangey pink sapphire. The pictures below show a stone full of inclusions and fractures/fissures with blue/yellow flashes (Figure 1) similar to the new lead-glass fracture-filled ruby.

The X-radiograph images also revealed high-density area (brighter colour in the negatives) along fractures and fissures (Figure 2). The high density areas with brighter or whiter features are normally the results of having heavier elements in composition compared to silica or alumina glasses. The chemical analysis by EDXRF spectrometry technique has also revealed that the chemical compositions of the filling substance showing the presence of lead (Pb) beside other usual trace elements in corundum (Figure 3).

New Blue Treated Sapphire

Preamble
The treatment technique of ruby and sapphire in Thailand has been continuously developed from the simple methods in the early days to the more complicated techniques in recent years. In September 2007, five faceted sapphire samples and few rough stones of similar material were submitted to the GIT Gem Testing Laboratory (GIT-GTL) from a gem treater who informed us that the sapphires were heat-treated by a new method.

General Observation
From the external appearance, those faceted sapphires were dark blue and semi-translucent (Fig. 1). Microscopic observation revealed many of rounded tiny blue inclusions oriented along large numbers of healed fracture. These inclusions, which were the main cause of color in the gems, seem to be the residue material remaining after the fractures were healed during high temperature heat treatment. The internal diffusion feature was not found in these new materials (Fig. 2). In general, the gems had the refractive index of 1.760-1.768 (0.008), the specific gravity of 3.94, exhibited red emission under the Long Wavelength Ultraviolet (LW/UV) light and weaker under the Short Wavelength Ultraviolet (SW/UV) light. Besides, red emission was found when shining with the high density light (Fig. 3).

The Analyses Using Advanced Instruments
From the chemical analysis by EDXRF technique, it was found that there were cobalt (Co) and lead (Pb) presented as impurities among the other elements (Al, Fe, Ti, Ga) commonly found in sapphire (Fig. 4). The UV-VIS absorption spectrum showed the main absorption peaks at approximately 630 and 530 nm (Fig. 5). This absorption pattern was totally different from the absorption due to Fe-Ti intervalent charge transfer usually occurred in blue sapphire. In fact, the absorption characteristic mentioned above was similar to the absorption of cobalt which was found in glass or synthetic blue spinel. From the infrared absorption analysis, it was found that the absorption spectrum was clearly different from other corundum (Fig. 6).

Conclusion
In conclusion, it was likely that the raw material used for this technique was the semi-translucent pale colored sapphires consisting of many cracks .The treatment process was a high temperature heating technique involving cobalt and lead containing flux. The color of gem was mainly due to the inclusions of blue cobalt-bearing solid residues left along healed fractures after the high temperature treatment.

Acknowledgements
In this study, the GIT would like to express our grateful thank to Mr. Tanusorn Lethaisong and Ms. Sasitorn Boongkawong who kindly provided us the samples and their willingness to let us disclose the new treatment technique in order to sustain the 'consumers' trust and confidence in his new product.

Update on an Uncommon Lead-Glass Treated Ruby

In August 2007, the Gem Testing Laboratory of Gem and Jewelry Institute of Thailand (GIT-GTL) received one unusual lead-glass treated ruby we ever found. This 9.07 ct ruby (Figure 1) shows a mosaic-like surface feature apparently comprising ruby fragments cemented by lead-glass matrix (see Figure 2, under dark field illumination). It is better seen under reflected light (Figure 3) in which the ruby appears light grey while the lead-glass is dark grey as a result of differences in lustres and hardnesses. Obviously the surface texture of the stone displays somewhat unmatched pieces and, in part, optically uneven orientation of many fragments. These textural features seem to suggest that this ruby is rather a composite stone than a single crystal fracture-filled with the lead glass as commonly found in many glass-filled rubies.

The basic gemological properties of this stone are similar to those of common ruby except its specific gravity (SG) which is about 4.20. This value is somewhat higher than the normal range of corundum (~ 4.00), and is certainly due to the influence of very high amount of lead-glass in the stone. The qualitatively chemical analysis using EDXRF also reveals a pronounced lead (Pb) content (Figure 4). The FTIR Spectrum of this stone shows two exceptionally strong broad absorption bands in the range between 2,200 – 3,800 cm-1. Such the absorption bands, nonetheless, are comparable to those of the artificial glasses detected in the glass-filled ruby (Figure 5).

Based on the features and evidences presented above, the GIT-GTL, as a member of the Laboratory Manual Harmonization Committee (LMHC), discloses such a material with the following comment: "A composite made up of ruby and (lead) glass". So for the GITGTL has not received any stone with such as similar feature again.This may due to the uncommon nature of this type of stone in the market or they might have been sold at a reasonably low price without certification.

Rubies with Unusual Characteristics

Since November 2007, the Gem Testing Laboratory of Gem and Jewelry Institute of Thailand (GIT-GTL) has received a number of ruby samples said to be originated from Madagascar. Microscopic examination reveals some unusual internal features, such as wispy veil-like fingerprints filled with quite dense fluid, numerous tiny clusters of colourless inclusions and isolated colourless crystal inclusions which could not yet be identified by Raman spectroscopic technique (Figs.1-2).

All of those stones show strong red luminescence in LWUV. The chemical analyses by EDXRF indicate rather high chromium contents (0.43-1.54 wt% Cr2O3), moderate-to-high iron contents (0.04-0.49 wt% Fe2O3), very low-to-low titanium (0.007-0.014 wt% TiO2) and vanadium (0.000-0.016 wt% V2O5) contents, and moderate-to-high gallium contents (0.006-0.046 wt% Ga2O3) in those samples.

The absorption spectra in IR range show no OH-related peaks in those samples. In contrast the UV-Vis-NIR absorption spectra show not only the strong Cr absorption bands and lines as normally expected for a ruby sample but also an unusual broad absorption band centered at around 900 nm, which normally appear in basaltic-related sapphires. This extra absorption band may possibly related to Fe2+ /Fe3+ charge transfer in which its intensity seems to be directly related to the amount of Fe in the sample (Figs. 3-5).

This unusual absorption band has not been so far observed in natural rubies, not even in rubies containing equally high Fe contents from basaltic-type origin (e.g., about 0.442 wt% from Africa; see Fig. 6).

With such the suspicious internal features including undeterminable inclusions and the presence of absorption band at around 900 nm, these, to us, are quite ambiguous evidences and are uncommon characteristics being found in a natural ruby Because of the aforementioned reasons, the GIT-GTL needs to make further in depth investigations on those samples. We, therefore, regret to temporarily suspend issuing of the report on the authenticity of this type of ruby samples for the time being. We remain in touch with our clients soonest on the progress of our investigations.

We would also request stone dealers and/or individuals who may come across or have experiences with such ruby samples or rough of the same material to contact us or one of members of LMHC. So far the GIT-GTL still has not yet received any information related to our requests. We thank for your kind cooperation and responsibility.