The Mogok Valley in Upper Myanmar has produced some of the finest rubies but, in recent years very few good rubies have been found there. The unique colour in Myanmar (Burmese) rubies is described as "pigeon’s blood". They are known in the trade as “Mogok” rubies. In central Myanmar the area of Mong Hsu also produces rubies. The latest ruby deposit to be found in Myanmar is situated in Nam Ya.

Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems only diamond is harder (Mohs 10.0 by definition).

All natural rubies have imperfections in them, including colour impurities and inclusions of rutile needles known as "silk". Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics or substitutes. Usually the rough stone is heated before cutting.

Almost all rubies today are treated in some form (of which heat treatment is the most common practice), and rubies which are completely untreated and still of excellent quality command a large premium.

Improvements used include colour alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them. Prices of rubies are primarily determined by colour (the brightest and best "red" called Pigeon Blood Red, command a huge premium over other rubies of similar quality).

Clarity follows colour: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions will indicate the stone has been treated one way or another. Cut and carat (size) also determine the price.

Myanmar has long been known as the best source for rubies in the world, gemstones whose beauty is rivalled only by the emeralds produced by the mines of Colombia.

During the Bagan (Pagan) Dynasty (1044 to 1287 CE) rubies were worn by Myanmar royalty. Some of the royal rubies were so valuable that a Chinese emperor is said to have offered a city in his own country in exchange for one of the prized gemstones.

Rubies were used in ceremonies and to adorn royal regalia, and the choicest items mined were reserved for the court. Some were sold to India and the Middle East, but many of the finest rubies and other gemstones were dedicated to the Buddhist religion.

Myanmar people follow Theravada Buddhism, which preaches the virtues of humility and living a simple life without ostentation. The gems were therefore not used for personal adornment but were encased in the htarpanar-taik, or relic chambers of pagodas and stupas. The search for these riches was one reason why more than 1000 pagodas were desecrated and destroyed by British troops at the end of the Third Anglo-Burmese War.

European traders first visited Myanmar around 1400 CE with the primary aim of engaging in the spice trade. But some early travellers – such as Nicola di Conti, Ludovico di Varthema, Hieronimo de Santo Stephano and Caesar Fredericke – reported on the profusion and quality of rubies and other gemstones worn by Myanmar royalty, and this aroused the interest of the West.

At the end of the Third Anglo-Burmese War, the recently deposed King Thibaw was persuaded to entrust the crown jewels and the Nga Mauk ruby to a Colonel Sladen for safekeeping. Later, when Thibaw asked for the return of the ruby, he was told that Sladen had returned to England. The British authorities finally told Thibaw that Sladen had died in 1910 and that there was no record of him handing over any ruby of quality to the government. Many Myanmar believe to this day that Thibaw was given the run around and was the victim of deceit in high places. No trace of the Nga Mauk ruby has surfaced since.

After the British annexed Myanmar, international interest grew in the ruby mines at Mogok, known to be the richest in the world. There was fierce competition to acquire mining concessions. In 1889 a company called Burma Ruby Mines Ltd won a lease to work the mines. However, due to their reliance on heavy equipment and machinery the venture failed and the company went into voluntary liquidation in 1934. Another company, Ruby Mines Ltd, took over. When the Japanese invaded Myanmar the managing director and staff fled to India.

Myanmar regained independence after World War II. Not much was accomplished in gem mining and the gem industry was nationalized in 1962. When the State Law and Order Restoration Council took over the reins of government in 1988 it repealed the old laws, adopted a free market policy and threw open the doors to private enterprise and direct foreign investment.

The Ministry of Mines set up a new agency called the Myanma Gems Enterprise to oversee the changeover. Under the enterprise the gemstone industry was liberalized, joint venture agreements were signed between the government and ethnic groups inhabiting the gem-bearing areas, and private companies were allowed to import machinery and equipment without paying customs duty.

These measures led to an increase in the number of local gem companies. In 1995 224 new licenses were issued, boosting the exploration and production of gemstones and heavily fractured Mong Hsu rough rubies.

Mong Hsu is located in Shan State, about 150 miles east and slightly to the south of Mogok. The mine there was worked in the 19th century, but since the rubies obtained were usually opaque and could not be easily faceted, work in the area was largely abandoned.

The discovery by the Thais that Mong Hsu rough rubies, when subjected to intense heat, take on the colour of Mogok rubies changed all that. Soon monstrous quantities of rough rubies from the region were being sold at gem auctions. In March 2002, more than five million carats of Mong Hsu rough rubies were purchased, while sales of genuine Mogok rubies languished.

Thai gemstone “cookers” are constantly experimenting with heat treatments to enhance the quality of rough stones. They have already achieved considerable success and flooded the market with all kinds of heat-treated stones.

The Myanmar government has taken pains to assure potential buyers that all the rubies and sapphires sold at the Myanma Gems Enterprise auctions and Union of Myanmar Economic Holdings Ltd auctions are natural and untreated, and that the Mong Hsu rough rubies offered for sale are untreated unless otherwise stated.

The question of provenance or place of origin has lately come to the fore with regard to rubies. Myanmar rubies are the finest in the world, against which all others are measured, and to be able to say that a particular stone comes from Myanmar enhances its value by 10 to 20 per cent over those of similar quality from other sources.

Formerly there was no sure fire method of proving provenance, the method being chancy and based on anecdotal evidence. However, a new technique using DNA fingerprinting has been developed. The water in which emeralds, rubies, sapphires and other precious gems were crystallized millions of years ago varied widely from area to area in the presence and quantity of certain minerals. The DNA process takes a small sample of the surface of the stone, vaporizes it and measures the oxygen isotope ratio, which can be used determine with certainty from which mine a given gemstone came.