Ruby is a mineral of very limited distribution. The name used in mineralogy is Olivine, because of its olive green colour. Peridot was brought to Central Europe in the Middle Ages by the crusaders and was often used for ecclesiastical purposes. It was the most popular stone during the baroque period. In the 1800's, it was determined that sapphire and ruby are gem varieties of corundum.
Sapphires come in a variety colours such as green, yellow, blue, white and pink.
The most significant deposits are in Australia, Burma and Thailand. In 1984 sapphire deposits were discovered in Montana, United States. The name is derived From an Indian word for stone . In ancient times, opal was included among the noble gems and was ranked second only to emerald by the Romans. In the Middle Ages, it was supposed to be lucky, but in modern times it has been regarded as unlucky.