There are two types of ruby deposits, primary and secondary. A primary deposit is where a gemstone forms and is still imbedded in the ground or host rock where it formed. A secondary deposit is deposits of a gemstone along a riverbed when the river has eroded a primary deposit and washed the stones downstream. Most ruby is mined from secondary deposits. Secondary ruby deposits are typically mined with process that are very simple and inexpensive where as primary deposits often require heavy equipment and explosives making much more costly. The most well know source of rubies is Burma (known today as Myanmar). Today, due to political situations and human rights issues there is an embargo on all imports from Myanmar. Rubies mined in Myanmar that were imported into the United States prior to the embargo may still be legally bought and sold. Burmese rubies have long been regarded as the best in the world. There are two main deposits in Myanmar; Mogok and Mong Hsu. Mogok tends to produce the finest rubies with superb color and strong florescence. Rubies found in the Mong Hsu area tend to be of lesser quality and typically the center of ruby crystals found here are dark and must be heat treated to improve the color. Again, there is currently an embargo against stones from both Mong Hsu and Mogok and it is illegal to import anything from Myanmar. Stones that entered the United States prior to the embargo may still be legally bought and sold. In the 1960s a coup in Myanmar disrupted ruby production in the area and the demand for ruby was filled by Thailand and Cambodia. Today ruby sources in Thailand and Cambodia are almost totally depleted. Though Thailand is no longer a major producer of ruby it is still a major center for ruby cutting and trade. Some fine quality ruby comes from Sri Lanka. Sri Lanka is more well known for sapphires and many people in the gem industry would call many of the rubies that come from Sri Lanka Pink sapphire. The Sri Lankan government has banned mechanized mining limiting miners to primitive methods. Vietnam is also currently an important ruby source producing fine quality rubies that have often been mistaken for rubies from Mogok Myanmar. Manny rubies from Vietnam contain blue patches and these rubies are often heat treated to remove or diminish these blue patches.