Eversince the ancient times, a strong relation was established between someone's month of birth and a precious stone, called therefore “stone of the month of birth” or Birthstone. Aaron's pectoral included 12 precious stones symbolizing the 12 tribes of Israel or the 12 months of the year, but it is from the renaissance that the custom of wearing the stone of someone's month of birth expanded in Europe.
From these times, several new gems have been discovered, such as the Alexandrite and the Tanzanite, and has joined traditional stones. Today birthstones are gemstones: precious stones, semiprecious stones and one of animal origin: the pearl.
The stone of the month of birth in january: the Garnet
It is more like it to say “garnets” since the term garnet includes several gems of different colors:
The stone of the month of birth in February: the Amethyst
The stones of the month of birth in March: the Aquamarine
It's the blue variety of the Beryl (the green beryl is the emerald, the pink beryl the morganite, the golden beryl the heliodor)
The stone of the month of birth in April: the Diamond
The stones of the month of birth in may: the Emerald
It's the green variety of the Beryl, one among the 4 precious stones (diamond, ruby, sapphire, emerald). The emerald often contains inclusions called “the garden of the emerald”.
The stones of the month of birth in june: the Alexandrite, the Pearl and the Moonstone
The stone of the month of birth in july: the Ruby
The stones of the month in august: the Peridot
It's a green gemstone, long called the emerald of the poor. The peridot is more and more searched by jewelers.
The stone of the month of birth in september: the Sapphire
The stones of the month of birth in october: the Opal and the Tourmaline
The tourmaline or rather “tourmalines” since the term includes different colored stones. There are tourmalines of different colors but the most rare are called Paraiba: they are neon-blue.
The stones of the month or birth in november: the Citrine and the Topaz
The topaz is a gem searched in different colors: yellow gold, blue, colorless and the most rare among topazes is the imperial pink topaz
The sones of month or birth in december: the Tanzanite, the Turquoise and the Zircon
The tanzanite is one of the latest discoveries of gemstones... blue colored, it's the most sold blue gemstone after the sapphire.