Rubies are known for being the birthstone for July and are one of the most prized gemstones. Ruby is also used as the stone for 15th and 40th marriage anniversaries. Rubies are known for their hardness, durability, luster, and rarity. Large rubies are hard to find and are therefore more valuable than diamonds of the same size.

The Ruby was named for the Latin word 'ruber' which means red. Ruby's day is said to be Tuesday, its season summer, and its apostle St. Matthew. Eastern legends believe that rubies contain the spark of life "a deep drop of the heart's blood of Mother Earth." Some ancient Orientals believed that the ruby is self-luminous and called it "glowing stone" or "lamp stone." It is believed that the Emperor of China used a ruby to light his chamber. Hindu priests believed that the homes of the gods were lighted by emeralds and rubies. Greek legends also speak of ruby. It was said that a female stork repaid Heraclea for her kindness by bringing her a ruby so bright that it illuminated her room at night. Ancient Hindus, Burmese, and Ceylonese believed that rubies ripen with age. The believed that sapphires were unripe rubies and that inclusions in stones meant that they were overripe. Rubies were thought to bring good health, guard against wicked thoughts, amorous desires, and disputes during the Middle Ages. Red stones including rubies were thought to cure bleedings. A stone which turned darker was thought to warn its owner of coming misfortunes, illness, or death.

Until about 1800 all red gemstones were called rubies. Later this changed and many stones which were thought to be rubies were in fact red spinel, red tourmaline, and red garnet. An example of this is the "Black Prince's ruby" in the English State crown that was thought to be a ruby, but in fact is red spinel.