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Synthetics

Ruby 'the Lord of the Gems' is desired for its rarity and beauty. Acquiring its name from Latin word 'Rubeus' it symbolize love and passion. It is the red variety of mineral corundum with colors ranging from purplish to bluish red to a yellowish red. However the finest variety of ruby has vivid red color with the faint undertone of blue as found generally in Burmese rubies. Ruby due to their sturdiness and beauty makes a fine choice for any piece of jewelry. It is an accepted birthstone for the July -born individuals.


Passion for rubies led to their mass production in the laboratories. A.V Verneuil was the first one to create synthetic ruby using flame fusion method in the late 1800s. These rubies are not considered natural since they are made in laboratory. Nowadays new techniques are used to produce synthetic rubies like Kashan ruby and Chatham ruby which are so close to their natural counterparts in all properties like crystal structure, trace elements, color and hardness that it requires careful observation by a qualified gemologist to distinguish them from natural rubies.

The two most common methods are - Flame fusion and Flux fusion process. The first method is flame-fusion process through which ruby is grown by dropping powder into a flame and freezing it into a synthetic ruby crystal. These stones show curved striae (curved color banding), gas bubbles and flecks of aluminum powder which are not found in the natural rubies. Pulled ruby is technically identical with flame ruby. It is a process in which melted ingredients are dripped into a boule and then allowed to cool at room temperature and pressure to crystallize. By this process rubies are grown very quickly but they do not look glassy therefore easier to separate from the natural stones. They are used extensively in imitation and lower priced jewelry etc. 

The second process is the flux growth process which takes longer time, usually months to produce rubies which can pass of as real ones. The crystal structure duplicates flux or the molten chemical. These rubies have inclusions which are found in the natural corundum. These form stress fractures when pressure is released during the manufacturing process. The fractures are then filled with growth solutions healing the fractures but leaving behind a pocket of undigested flux. These fluxes resemble feather or fingerprint inclusions or small specks of platinum which appear to have come from the crucible on which the crystals were grown. The difference in the refractive index of the flux to the corundum makes the flux stand out and help in identifying the ruby as synthetic .The flux inclusions can appear coarse in comparison to the natural inclusions. These stones are cut to near ideal proportion and appear flawless to the naked eye. Unlike flame fusion rubies, these let light bounce around .Flux grown rubies are expensive due to long growth time and low production yield. 

Some of the synthetic rubies include Douros from Greece, Chakravorty, Ramaura, Kashm and Chatham which are exceptional in beauty and fineness.

Kashan Rubies are flame grown showing parallel rod like solid filled, coarse negative crystals which are granular or sugary in nature having high degree of reflectivity. The crystals show wispy pattern resembling rain drops or comets. These contain varying amounts of iron-oxide .Their color is close to many Thai rubies with strong orange dichroism.

 
KashanTM Synthetic Ruby Crystal.

Douros Rubies are produced in Greece and are available since 1995.These are made using flux method in which synthetic magma (flux) is grown under conditions similar to those found in nature. These have attractive visual appearance and reflect high degree of transparency. Their pure red colour surface show hexagonal crystal structure.

* Judith Osmer discovered the process of growing gems after 25 years of sustained research and came up with Ramaura Rubies. These are grown by flux technique in controlled high temperature with molten magma. It is grown spontaneously without a seed with natural inclusions, veils, comet tails, conically shaped feathers, growth lines and color zones. The inclusions consist of various forms of flux particularly coarse orange-yellow flux and white flux fingerprints. These features help in identifying Ramaura Rubies as synthetic. Another distinct feature is presence of fluorescent zoning which occurs in the areas just below the surface. Its intensity varies from high to very high and color ranges from sulphur yellow to yellowish orange to nearly pure orange.

Ruby doublets are produced by using synthetic or imitation backing with a natural corundum crown. It is often possible to detect them through the glue which joints two pieces together. They show natural inclusions like features and crystals.

Chatham Rubies came into market as early as 1940s when young Carol Chatham from San Francisco discovered the secret of growing gems in a laboratory. These rubies have features including various form of flux residue. These residues are usually opaque white globules, mesh like patterns and tightly arranged white fingerprints. They reflect hexagonal, triangular, rectangular and spiky platinum platelets which reflect slivery light. The other inclusions are transparent crystals, hammock shaped and net like intertwined feathers.

Chakravorty Rubies are also made through flux process.

 

 
ChakravortyTM Synthetic Ruby Crystal

 

Knischka synthetic Rubies developed by Prof P.O Knischka can be identified through their spindle shaped multifaceted shape. Other internal features include swirls of colour, irregularly shaped with net like liquid feathers. They show black hexagonal platelets of platinum and silver. The most distinguished feature is two-phase inclusions .The absorption band between 250 and 440 nm indicate that the ruby is synthetic.


Synthetic rubies can be extremely beautiful and affordable. But since they are not natural, they are not considered as gemstones. Besides they can never capture the magic and aura of the real rubies
Czochralski
Flame fusion
At first, Verneuil synthetic rubies were annealed to relief the stress built up in the boule as well as to diffuse the curved striations to complicate detection. At the beginning of 1990s, many heat-treated Verneuil synthetic rubies were sent to gem market while natural rubies from Vietnam appeared on the market. The Verneuil synthetic rubies had been traditionally easy to identify under magnification test with their characteristic curved lines, however, heat treatment induced feathers with liquid-like appearance in the stone and this made the material much more difficult to identify.

Floating zone
Dentritic metallic inclusions; platinum platelets.

Flux
Chatham synthetic Ruby

Internal diagnostic features include various forms of flux residue (opaque white globules, mesh-like patterns and tightly arranged white fingerprints); platinum platelets (hexagonal, triangular, rectangular and spiky) which reflect light with a silvery lustre; thick angular platinum crystals; white cloud-like areas (composed of a dense concentration of minute particles); transparent crystals; hammock-shaped and net-like intertwined feathers; and colour zoning.

Kashan synthetic Ruby

The Kashan synthetic ruby has been back in the market after many years of absence.

In the early 1960s stones it was possible to identify traces of the seed crystal within the gem. Feather-like structures similar to those seen in synthetic flux-fusion emeralds, and a dot-dash pattern of droplet-like inclusions were often present. These stones sometimes contained inclusions that resembled the marks made when a loaded paint brush is slapped on a wall (the so-called "paint splash" inclusions).

The later 1970s Kashan rubies often contain solidfilled, coarse negative crystals (which contain a granular or sugary material and have a high degree of reflectivity); clusters of parallel, rod-like, solid-filled negative crystals; wispy patterns resembling rain drops ("rain" or "dust" inclusions); and rain-like structures resembling comets.

Silk is rarely present, and then only appears as single, isolated filaments or needles. The presence in a stone of significant quantities of silk is evidence that the ruby is not a Kashan.

Because Kashan rubies contain varying amounts of iron oxide, their S.W. U-V transmission factors overlap those of natural rubies. The colour of most Kashan rubies is reasonably close to that of many Thai rubies, and in comparing the two, it's worth noting that most Kashans show a stronger orange dichroism than Thai rubies.
Heated Kashan synthetic rubies hit the market in the mid 1990s. These were quite large (2ct to 27ct) crystals and considerable amount have presumably be distributed(see GEMMOLOGY 1996, Nov). 

Ramaura synthetic Ruby
 
Opening the door to the crucibles.

1000-degrees centigrade crucibles in the furnace.

Removing the crucibles from the furnace.

Judith pouring molten flux off the rubies attached to the platinum crucible.

The red-hot flux is the same temperature as molten lava.

The crucibles cooling to room temperature.

Opening a crucible and removing excess hardened flux.

The rough rubies grown on the bottom of the crucible.

Rubies in their natural hexagonal form, knocked out of the crucible with a mallet.

The beautiful faceted and polished Ramaura Rubies

These stones are manufactured by JO Crystal Company in California. Inclusions consist of various forms of flux, particularly coarse orange-yellow flux and white flux "fingerprints".

These features, together with colour zoning, "comet tail" inclusions and conically shaped feathers can provide conclusive proof of synthesis. Another identifying hallmark of the Ramaura ruby is the parallel graining or growth lines, also described as the "Scotch in water" or "heat wave" effect.

What may, however, prove to be the main identifying feature of the Ramaura ruby is its fluorescent zoning under L.W. U-V; the manufacturer claims to have introduced a rare-earth dopant to make the stone more easily identifiable when exposed to U-V.

This fluorescent zoning occurs in thin areas just below the surface. It varies from intense to very intense, and has a colour that ranges from distinct sulphur yellow through yellowish orange to a nearly pure orange. Although generally quite thin, these zoned areas also possess a dull; chalky translucent appearance. Unfortunately, some cut stones have been seen that don't possess this tell-tale fluorescence.
Synthetic rubies that show features of Ramaura ruby have been heated in 2005 and this is raising a new problem in ruby identification.
Knischka synthetic Ruby

Developed by Prof. P.O. Knischka, the synthetic ruby is recognizable in the rough crystal by its spindleshaped, multi-facetted shape. Facetted stones (these aren't yet widely distributed) may contain phantom-like clouds of dust particles (similar to those seen in Burma rubies).

Other more diagnostic internal features include swirls of colour; irregularly shaped, net-like liquid feathers; parallel negative crystals having- the same bipyramidal habit as the host crystal and appearing at the end of long crystal tubes; black, distorted hexagonal platelets of platinum and silver; and two-phase inclusions (with ill-defined void boundaries and conspicuous bubbles), this last feature being regarded as an identifying characteristic of Knischka rubies.

When visible on a spectroscope, an absorption band between 250 and 400 nm is a clear indication that the ruby is a synthetic (this band is more easily detectable on a spectrophotometer). The Knischka rubies that have been inspected so far show little iron content, and therefore have a high S.W. U-V transmission factor.  (Peter G. Read)
Douros Synthetic Ruby
Flux that was mainly composed of lead is used for Douros ruby.
Novosibirsk(Russian) 
Hydrothermal

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