A birthstone is a gemstone that represents a person's period of birth that is usually the month or zodiac sign. Birthstones are often worn as jewellry or as a pendant necklace.
In 1912, in an effort to standardize birthstones, the (American) National Association of Jewelers (now called Jewelers of America) met in Kansas and officially adopted a list. The Jewellry Industry Council of America updated the list in 1952 by adding Alexandrite for June, citrine for November and pink tourmaline for October. They also replaced December's lapis with zircon and switched the primary/alternative gems for March.