A VERY RARE RUBY AND DIAMOND RING

A VERY RARE RUBY AND DIAMOND RING
Set with a cushion-cut ruby weighing 5.61 carats enhanced by a pavé-set twin border of brilliant-cut diamonds, to the quarter-hoop, mounted in 18K yellow gold, ring size 7
Accompanied by a report from the Gübelin Gem Lab, stating that the 5.61 carat natural ruby is red color, originates from Thailand (Siam) and has no indications of heating, report no. 12055308, dated 14th May 2012
Accompanied by a report from the American Gemological Laboratories, stating that the 5.61 carat natural ruby is red color, originates from Thailand and has no gemological evidence of heat, report no. CS 55454, dated 25th June 2013
On Thailand Rubies
‘Thailand’s ruby mines inhabit a corner of the country’s eastern region, in Chanthaburi and Trat Provinces, actually stretching across the border into the Pailin area of Cambodia. They have been known from early times, the earliest known reference being that of the Chinese travelers, Ma Huan (馬歡), in 1408 AD.
It was events in the 1960s which propelled the region to prominence in world ruby markets. In 1969, Ne Win’s disastrous military government annexed Burma’s famed Mogol ruby mines. Suddenly, the world was deprived of its traditional source of ruby and forced to look elsewhere. Their ravenous gaze settled on the stones produced along the Thai/Cambodian border…… And with improvements in heat treatment, it was not long before the mines supplanted Burma as the world’s major ruby supplier.’
~ Richard W. Hughes,
1996
Thailand's ruby deposits became the major source for fine rubies in the 1980s, after the annexation of the Burmese Mogul ruby mines by the country’s military government. Due to senseless exploitation, those mines in Thailand have become extinct, hence no longer producing today. As such, over 90% of Thai rubies on the current market have undergone technical heat treatments to bear on the remaining deposits, rendering unheated stones extremely rare.
Most Thai rubies tend to have a garnet-red color and lack of fluorescence effects due to high iron content inside the material. The top quality Thai rubies can be remarkably clean, high crystal, and excellent clarity. In the old days, Thai rubies have been extensively used in the royal jewels of Thailand. A few connoisseurs would agree that the Thai ruby is the “King of the gem.” Generally, they have good degree of transparency, cleaner and brighter than stones from Burma.
Oftentimes those unique characteristics have advantages over other sources of rubies. One key reason is that their roughs come in larger sizes and shapes, enabling the stones to be cut in spectacularly fancy shapes, including heart, marquise and emerald-cuts. Another proof of this present unheated Thai ruby is extremely rare,
because it is no longer possible to buy any even at very high prices, as the last ruby mine in Thailand has been mined out.