<P> Some rubies show a three - point or six - point asterism or "star". These rubies are cut into cabochons to display the effect properly . Asterisms are best visible with a single - light source and move across the stone as the light moves or the stone is rotated . Such effects occur when light is reflected off the "silk" (the structurally oriented rutile needle inclusions) in a certain way . This is one example where inclusions increase the value of a gemstone . Furthermore, rubies can show color changes--though this occurs very rarely--as well as chatoyancy or the "cat's eye" effect . </P> <P> Generally, gemstone - quality corundum in all shades of red, including pink, are called rubies . However, in the United States, a minimum color saturation must be met to be called a ruby; otherwise, the stone will be called a pink sapphire . Drawing a distinction between rubies and pink sapphires is relatively new, having arisen sometime in the 20th century . Often, the distinction between ruby and pink sapphire is not clear and can be debated . As a result of the difficulty and subjectiveness of such distinctions, trade organizations such as the International Colored Gemstone Association (ICGA) have adopted the broader definition for ruby which encompasses its lighter shades, including pink . </P> <P> The Mogok Valley in Upper Myanmar (Burma) was for centuries the world's main source for rubies . That region has produced some exceptional rubies, however in recent years few good rubies have been found . In central Myanmar, the area of Mong Hsu began producing rubies during the 1990s and rapidly became the world's main ruby mining area . The most recently found ruby deposit in Myanmar is in Namya (Namyazeik) located in the northern state of Kachin . </P> <P> Historically, rubies have also been mined in Thailand, in the Pailin and Samlout District of Cambodia, as well as in Afghanistan, Australia, Brazil, Colombia, India, Namibia, Japan, and Scotland; after the Second World War ruby deposits were found in Madagascar, Nepal, Pakistan, Tajikistan, Tanzania, and Vietnam . In Sri Lanka, lighter shades of rubies (often "pink sapphires") are more commonly found . The Republic of Macedonia is the only country in mainland Europe to have naturally occurring rubies . They can mainly be found around the city of Prilep . Macedonian rubies have a unique raspberry color . The ruby is also included on the Macedonian coat of arms . A few rubies have been found in the U.S. states of Montana, North Carolina, South Carolina and Wyoming . </P>

Where do most of the worlds rubies come from