The Miracle of Flame and Gemstone

 The Miracle of Flame and Gemstone

       During the volcano eruption, magma rises rapidly through the crack and fissure of the earth crust.  Some rocks, mineral and gemstones on the way of the magma canal may be ripped and carried out to the surface. Besides, the invading magma to the local host rock rises the temperature of the surrounding.  In the condition of high pressure and high temperature, the gemstones, minerals or even the rocks themselves are gradually altered in the level of atom. This slow alteration process may take millions of year to complete in their metamorphism. In gemstones, the alteration in their atom results in giving the improvement of clarity and color.

      This theory of gem alteration in the heating atmosphere is confirmed by chance or by accident as in the case of Chantaburi (the eastern province of Thailand) when the city caught fire in 1968. The destructive conflagration had destroyed whole city market including all gem and jewellery shops. In the center of the fire, the temperature may normally rises above 600^oc and can go higher if the fire persists for a longer time. At this temperature, gold is melt and diamond (as polymorph of carbon) will react to oxygen and be burnt to ash. After the fire was extinguished, villagers went to the site searching for the remaining objects. Surprisingly, they came across some corundum gems scattering in the ashes and others in the burnt safe. All these gemstones were neither burnt nor damaged by the fire (they remained in intact condition). They observed furthermore that the former packet of somewhat low-grade gems kept in the burnt safe, had been much altered in property: the gems that once used to have heavy inclusion of  black spots and minute particles became clean and more transparent, and the former color that used to be pale and mottled with color zoning was then transformed  to beautiful and even coloring. The villager assumed that it was the fire that had removed  the inclusion in gems and helped to improve their coloring and evenly distribute the coloring. That was a great discovery for gem alteration in Thailand and it was the starting point of Thai wisdom in gem alteration. Since then, villagers of Chantaburi carried out their experimental test with their gemstones until they achieved a suitable appropriate formula.  The only gem used by the villagers for the heat treatment is corundum (called as hard gems by people) because the melting point is 2,044^Oc (higher than any other natural gems). In the heating process, the temperature range is between 800-1,700^Oc that is far from the gem melting point, so there would be no damage to the gemstone. The result of gem alteration by heating give rise to the same result as the geological process by volcano, hence the result is permanent. We cannot verify if a gem has undergone heat treating or not by our naked eyes, especially, if such stone is clear from any inclusion. Thus the alteration process in the lab and geological metamorphism are identical.

Traditional Gasoline Oven vs.Computerized Electric Furnace
(Credit: krubannok.com)

     Each gemstone reacts differently to the heat treatment. Not every gems yield a desirable color. Similar to the natural process, the color quality of a particular gem depends on the presence of trace element in the gem ( chromophoric element). If there is no trace element at all, then the treatment will not result in any change of color. So the degree of color ( be it saturate, medium, pale or colorless)depends mainly on the chromophoric trace element already contained within the gem. This heat treatment is absolutely similar to the geological process.

     The furnace used for the heat treatment is compared to the magical time machine that reduces the time of the geological process (that may otherwise have taken millions of year to finish the evolution) to the human control. In one’s lifetime, how many time can one withness the volcano eruption from which the underground magma penetrates the cracks and rock cavities where gems are found?  That is beyond our imagination. Heating atmosphere (high pressure and high temperature) is the essential factor, both in the natural process and in the man-created process.  These 2 processes  give the same result: the beautiful color that is natural and permanent. The beauty of gems from both processes is equally durable and beyond time. When we understand this concept, we should not challenge the alteration of gem enhancement in the heating process any more.  All natural gemstones were altered by the heat involved geological process since the ancient time.  And then the man-created heating process in our era(of today) counterparts that of nature.

     In the later articles, I will go into the gem alteration techniques in more details regarding their categories and the methods which are used today.

                                                                                                             Siriwat Jiamanusorn (FGA)