Birthstones are stones which correspond to the month that you were born in (in the western world) and a piece of jewellery with a birthstone can make a special personalised gift.
Birth stones date as far back as the bible when they related to the signs of the Zodiac. A modern version was created in the 20th century in America. There are also birthstones which relate to Ayurvedic medicine in India and there is a mythical list of birthstones from Tibet.
Here’s a list of Birthstones:
January: Garnet, Hyacinth
February: Amethyst, Hyacinth, Pearl
March: Bloodstone, Jasper
April: Diamond, Sapphire
May: Agate, Emerald, Chaledony, Carnelian
June: Emerald, Agate, Pearl, Chaledony, Turquoise
July: Ruby, Carnelian, Onyx, Sardonyx, Turquoise
August: Carnelian, Moonstone, Topaz, Alexandrite, Sardonyx
September: Sapphire, Lapiz Lazuli, Coral
October: Opal, Aquamarine, Beryl
November: Topaz, Pearl
December: Turquoise, Ruby, Bloodstone
(The list is from the complete metalsmith and the historical references are from the internet.)