Your BirthStone.

The Birth-Stone.
It is the gemstone associated with the date of one's birth, the wearing of which is commonly thought to bring good luck or health.
Supernatural powers have long been attributed by astrologers to certain gemstones.
The stones now associated with each month, as listed below, have relationship to the ancient beliefs. Before mineralogy had progressed to the point of chemical analysis, colour was of greater importance than some of the other physical characteristics, and little distinction was made between emerald and chrysoprase, an apple-green powerful stone that brings luck, for example, or between ruby and garnet, or between citrine and topaz. When it came to the ability to heal or bring good luck, the actual stone and the look-alikes were regarded as equally effective. Even the names used in ancient times do not necessarily refer to the stones that go by those names in the 20th century; the sapphire of the ancient times is much more likely to have been lapis lazuli, the precious blue coloured gem, than what is now known as sapphire, and diamond was probably white sapphire or white topaz. In the 20th century the list was supplemented with a series of synthetic stones that were recommended as alternatives for some of the rarer, less-attractive, or less-durable natural stones.
January. Garnet. Dark Red PomegranateGem.
February. Amethyst. Violet variety of Quartz.
March. Blood-stone.
April. Diamond.
May. Emerald.
June. Pearl.
July. Ruby.
August. Sardonyx Pindot. Carnelian Agate.
September. Sapphire.
October Opal.
November. Topaz.
December. Turquoise Zircom.Opaque Greenish gem.