Tourmaline
cats eye
pinksapphire
SPINEL
Blue sapphire
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SRI LANKA GEMS
MONTH BIRTHSTONE ALTERNATIVE January Garnet Cinnamon Stone February Amethyst Alexandrite March Aquamarine Blue Topaz April Diamond White Sapphire May Emerald Green Sapphire June Cat's Eye Pearl July Ruby Pink Sapphire August Tourmaline Peridot September Sapphire Spinel October Opal Moonstone November Topaz Citrine December Star Stone Tourquoise
Blue SapphiresSri Lanka's Blue Sapphires are the finest in the world. The Blue Sapphire is second only to the diamond in hardness & is highly prized. Accordingly to the experts, Blue Sapphires with colours called "corn flower blue" & "royal blue tint" are of the finest quality. Sri Lanka's Gem Corporation exhibits a 93 carat Blue Sapphire of "cornflower blue".Star SapphiresThe 362 carat Star Sapphire being exhibited at the Sri Lanka's Gem Corporation is third largest Star Sapphire of such quality & colour. The most celebrated star sapphire of Sri Lanka called "Star of Bombay' is on permanent exhibition at Smithsonian museum of Natural history in New York."... and by some distressing impertinence the splendid Star Sapphire which is one of the glories of American Museum of Natural History's gem collection is called the Star of Bombay-not as it should be-the Star of Ceylon." Arthur C. ClarkeHeat treated Rubies & SapphiresIt is estimated that 90% of the rubies & sapphires in the world market today undergo heat treatment, a permanent process widely accepted by the gem trade. Sapphires are so common in Sri Lanka that the palest, least valuable gems were once used in ornamental rock gardens or buried under the posts of village homes for a blessing. These low quality sapphires, known as "gueda", were not suitable for setting into jewellery. But in the 1970s, Thai gem dealers perfected a heat treatment process that transformed the worthless gueda into valuable gems. By "cooking" the stones at high temperatures, they worked a kind of alchemy. The titanium dissolved & mixed better with the iron, deepening the blue colour of the geuda. The Thais then experimented on different coloured sapphires & rubies, & learned that a valuable sapphire or ruby could be made even more valuable by "burning" out slight flaws. The process is risky as certain stones may crack, melt or explode. In some cases, the gems lose all their colour.PadparadschaThe padparadscha is the most prized of the "fancy", non-blue sapphires. Padparadscha is a Sinhalese word derived from the Sanskrit "padmaraga", meaning lotus flower, & was first applied to sapphires in 1847. While lotus flowers occur in many colours, the original species is pinkish orange. A padparadscha sapphire is a delicate blend of these two colours. The effect is breathtaking-as magical as a tropical sunsets, padparadscha sapphires are exceedingly rare. Some sellers may try to pass off a pink sapphire as a padpardscha, but a true padparadscha calls for a harmonious blend of both colours, spread in a light, even tone throughout the stone. A stone may exhibit this perfect mix of colour when viewed from above, but when viewed from the side, shows a distinct separation of tones. Such a gem is simply a fancy sapphire & not the more valuable padparadscha. Many connoisseurs believe that a padparadscha sapphire can only come from Sri Lanka.Gemstone heat treatment
This oven is used in heat treatment to remove silkiness and Geuda to improve the color. Different stones are cooked at different temperatures for optimum quality. Oxygen is used to regulate the temperature of the oven. This oven comes as an electric model or a LP gas model(Lakmini furnace). The images shows a gas oven.
Heat Treatment of Geuda.
Classification of 'Geuda' is as follows:
a) Geuda:- Diesel(color of diesel fuel), Milky, Silky Geuda.b) Ottu:- Pita/Dot/Dun/Ural/Black/Atul Ottu
Sapphire is formed deep down below the earth's surface, some 65 kilometres down, and comes to the surface in a volcanic explosion in a 'formation tube' or vent. The sapphire comes up at the forefront of a volcanic eruption and is expelled with the pyroclast, or volcanic ash. This is typical for all Australian sapphire occurrences.
If the temperature in this formation tube is hot enough, and the residence time is long enough, the sapphire is clarified, on its journey to the surface. The main contaminant in sapphire is rutile (Iron - Titanium Oxide) and if the temperature/time relationship is sufficient this is volatilised and expelled from the sapphire or it is reabsorbed add reconverted within the crystal.
However, if the temperature is too low, or the rate of travel of the sapphire and pyroclast up the tube too rapid, the sapphire may be left with inclusions such as the "silk" veils which often cloud natural sapphire crystals.
The Thais developed the practice of commercial heat treatment many years ago to remove these silk veils to produce stones of improved clarity and brilliance This process has always been considered quite acceptable as no chemicals were added, and the holding of the sapphire at high temperatures to bring about this improvement was essentially only mimicking nature and was just finishing off what nature had started.
However, the heat treatment technology has been greatly extended in man's quest to turn lower quality material into brighter stone in the endless search for more profit - and some quite dubious if not actually false practices have resulted in recent years!!
A simplified explanation of the levels of heat treatment is as follows :-
a. Natural Untreated Sapphire.
This may be totally clear or may have small inclusions or silk bands. Whilst it was once the accepted practice to heat treat to remove all "silk', this is now not always done as a small quantity of silk is considered acceptable, if not actually desirable since untreated good quality material usually commands a premium price. We try not to heat treat wherever possible.
b. Simple Heat Treatment
This is considered quite acceptable in the jewellery trade as no chemicals are added and the sapphire is not changed chemically apart from the removal or conversion of the rutile and contaminant bonds.
This is a simple process brought about by a one-off heat treatment, and the resultant clarification of the sapphire is permanent and irreversible.
No radiation, chemicals or health risks are involved in this process.
c. Multiple Heat Treatment - Colour Generation
In certain cases, the amount of included material is too great to be removed by the simple one-off heat treatment process, So a system was developed of multiple heat treatments, sometimes in the presence of fluxing agents, which eventually lead to a clearer or brighter stone of acceptable colour.
The geuda/ottu stone is heat treated as many as six or eight times in order to clarify it and produce the pale "Ceylon Blue" which is sold at quite high prices - but is essentially a heat generated colour.
d. Bulk Chemical Diffusion - Beryllium Treatment.
The chemical diffusion process is carried out by multiple heat treatments of the sapphire in the presence of artificially introduced elements like beryllium or titanium, which penetrate the structure of the sapphire.
The beryllium treatment is carried out to produce golden, yellow, orange, apricot, padparadschas and similar colours from lower grade rough sapphire or from sapphire of less desirable colours. The beryllium can penetrate the sapphire to a considerable depth and can be difficult to detect.
The chemically modified stone may have good colour and brilliance, but it is no longer a 'natural sapphire' and cannot be sold without proper and adequate disclosure of the treatment it has suffered. It is essentially a "fake", albeit sometimes a very good one!!
The titanium treatment is carried out to enhance the colour and brilliance of blue sapphires, but the depth of penetration is far less than that for beryllium treatment and consequently repolishing of a stone may remove part of the chemically imparted colour.
Concerns have been raised as to the possible health risks arising from the beryllium treatment process, and these concerns are very real for the operators of heat treatment furnaces as the beryllium vapour is highly toxic.
Beryllium treated sapphire has only been present on the world markets - in the last two years or so, and it is still too soon to know whether the process may result in any long term health problems for the wearer of such chemically treated stones.