The ruby is exceptionally rare and considered one of the four precious stones, along with sapphires, emeralds, and diamonds. The color is caused by chromium, and the brightest and most valuable red is called pigeon blood-red. For centuries, the world’s main source of rubies came from Myanmar. They are also mainly found in Sri Lanka and Thailand. Rubies have always been held in high esteem in Asian countries, and there is early recorded transport and trading of rubies along the North Silk Road in China as early as 200 BC. July claims ruby as its birthstone.