The western birthstone chart is based on the biblical description of the breastplate of the high priest Aaron (brother of Moses) that consists of 12 stones that represent the 12 tribes of Israel. Across cultures and time, powers of protection were conferred to those who wore them. In 1912, the American national association of jewelers established a modern birthstone chart.

Month	Stones
January	Garnet
February	Amethyst
March	Aquamarine
April	Diamond
May	Emerald
June	Pearl or Alexandrite
July	Ruby
August	Peridot
September	Sapphire
October	Opal or Tourmaline
November	Citrine
December	Blue Topaz

The term garnet designates a family of gems that have identical crystalline structures. These stones are transparent and colorful. There are several garnets : pyrope (red to maroon), almandine (red to Gar violet), spessartine (orange to red-brown), grossular (green, yellow, brown, devoid of color), andradite (black, brown, brown-yellow), and uvarovite (emerald green). Informally, the term garnet is often used to designate pyrope and almandine garnets but also the red wine color. This stone is the birthstone of the month of January. A little bit of history: Garnets have been used in jewelry making for millennia, then known as carbuncles or red gems (pyrope, almandine).

They used to be known as semi-precious stone, however, this appellation was revoked because it was considered pejorative. Gemstones (also fine gem or gem) are translucent or transparent (topaz, quartz, opal, etc.). The following stones are classified as gems: amber, aquamarine, amethyst, citrine, rock crystal, cordierite, garnet, peridot, tanzanite, topaz, tourmaline and zircon. There are also ornamental stones such as lapis lazuli and turquoise, which are often mistaken as gemstones. This term generally designates opaque colored stones or stones of a lesser value. The reconstituted stones are manufactured by a process that reduces useless stones to a powder, the powder is then mixed with glue. Thus making a complete stone. Dyes can be added to give a certain uniformity to the stone's appearance. The term stabilized means that a natural stone, such as turquoise, was too porous and has been dipped in a resin bath, or into another protective lacquer, to solidify. In France, the only stones said to be precious are diamonds, sapphires, emeralds and rubies. Around the world, this term refers to any gem of great value.

Yag (yttrium aluminum garnet) is the name of a synthetic crystal used as a substitute for diamond. It is a very convincing imitation that was developed in 1969. Its name is derived from its composition. Yag is an yttrium aluminate of a crystallographic garnet structure (yttrium, aluminum, garnet).