Burma, also known as Myanmar, has been a source of some of the world's finest rubies for centuries. The Mogok Valley in northern Burma has been the most famous source of Burmese rubies since ancient times.

The history of Burma ruby dates back to at least the 6th century AD when they were mentioned in Sanskrit texts. The Burmese royal court was known for its love of rubies, and they were often used to adorn royal regalia. The Mogok Valley was under Burmese control until the British annexed it in 1886, and the British began mining the area in earnest in the early 20th century.

The composition of Burma ruby is primarily made up of the mineral corundum, which is a crystalline form of aluminum oxide. The presence of trace elements, such as chromium, iron, and titanium, gives the ruby its distinctive red color. In the case of Burma rubies, the presence of chromium is responsible for the deep, rich red color that is highly valued.

In addition to the mineral composition, the quality of a Burma ruby is also affected by the presence of inclusions, or tiny imperfections, within the crystal. In some cases, these inclusions can enhance the beauty of the ruby by creating a "silky" appearance that enhances the depth of color. However, too many inclusions can detract from the value of the ruby.

Fine quality Burma rubies are known for their vivid red color, which is caused by the presence of chromium in the crystal structure. The color of a Burma ruby is often described as "pigeon's blood" red, which is a deep, rich red with a slightly bluish undertone.

The rarity of fine quality Burma rubies is due to a combination of factors, including the limited size of the deposits, the difficulty of mining the rubies without damaging them, and the high demand for them. In addition, Burma rubies are subject to a US trade embargo, which has limited their availability in the global market.

Some of the most famous Burma rubies include the Sunrise Ruby, which is a 25.59-carat Burmese ruby that sold for over $30 million at auction in 2015. Another famous Burma ruby is the "Mogok Ruby," which is a 16-carat ruby that was once owned by the Burmese royal family.

Overall, Burma rubies are considered some of the finest and most desirable rubies in the world, prized for their rich color and rarity.