Many believe that the Breastplate of Aaron is the basis for the origin of birthstones.  The instructions for fabricating the Breastplate are in Exodus 28; 5-30 calling for the twelve stones of the Twelve Tribes of Israel to be set in four rows.  These gemstones corresponded to the zodiac signs of the time.  Our present calendar month system was not known at the time of Exodus. Today birthstones are more commonly associated with the calendar month of one's birth.

January - Garnet
Garnet is the traditional birthstone for the month of January. Garnets occur in every color of the spectrum except blue. Most common are the rich burgundy red to burgundy brown hues, making them a favorite addition to jewelry. Garnet is the suggested gem for the 2^nd and 6^th anniversaries.

February - Amethyst
This vibrant purple gemstone has been part of Royal Crowns and Scepters for centuries. Amethyst is the modern February birthstone and this variety of quartz remains popular today. It is the suggested gem for the 4^th, 6^th, and 17^th wedding anniversaries.

March - Aquamarine
These light blue to pale aqua blue gemstones are a variety of beryl, like the emerald. Associated with water, they are treasured by seafaring people. Aquamarine is said to symbolize safety and security and is the accepted gem for the 19^th wedding anniversary.  High quality aquamarine will be clear and bright in color and tone.

April - Diamond
Prized for centuries, diamonds have been treasured for their fire and brilliance.  The diamond symbolizes everlasting love and is accepted as the gem for the 10^th, 60^th, and 75^th wedding anniversaries. Look for a good balance of the four C's, cut, color, clarity and carat weight.

May - Emerald
A rich green, emeralds are prized around the world. A variety of beryl, flawless emerald specimens are extremely rare. Emeralds are suggested as the gem for the 20^th and 35^th wedding anniversaries. The ancients wore emeralds to enhance love and contentment and believed emeralds brought wisdom, growth and patience to those that wore them.  Today most quality emeralds come from Columbia.

June - Pearl
Pearls are an organic gem produced by mollusks.  Today nearly all are cultured and only about one in twenty mollusks will produce gem quality pearls. Pearls are a must for the well-dressed woman's wardrobe. Freshwater pearls are given on the 1^st wedding anniversary.  They are also given on the 3^rd, 12^th, and 30^th anniversaries.

July - Ruby
Ruby is the modern July birthstone. Like the sapphire, ruby is a variety of corundum which gets its red color from trace amounts of chromium in the stone.

August - Peridot
Peridot is a bright, vivid green and will add sparkle to any piece of jewelry. It is a gem variety of the mineral chrysolite or olivine.  The best colored peridot has an iron percentage of less than 15% and includes nickel and chromium as the trace elements. Said to signify strength, both individual and within a relationship, peridot is recommended for the 16^th wedding anniversary.

September - Sapphire
Sapphire is the modern September birthstone. A variety of corundum, sapphires are in the same family as the ruby. Most known for blue hues and dramatic highlights, sapphires are also a fabulous pink and very popular in jewelry. Sapphires are the gem designated for the 5^th, 23^rd and 45^th wedding anniversaries. It is the typically a star sapphire that is given for the 65^th wedding anniversary. Sapphires are a symbol of sincerity and faithfulness.

October - Opal
Opal is the modern October birthstone. There are two distinct types of opal, common and precious. The way the silica particles form determines type. In precious opal, silica particles are packed in regular rows and layers. Moving the stone causes light to diffract, or split as it touches the surface of the opal.  This light diffusion shows iridescent flashes of green, blue, aqua and sometimes a yellow-gold or red color known as 'fire'. There are many colors and varieties of opals, black opals being the most rare and valuable.  Opals are the accepted gem for the 13^th wedding anniversary.

November - Citrine
Citrine is the modern November birthstone. When heat treated, citrine becomes a fiery golden yellow-orange, dark orange-brown, or reddish brown. Natural citrine is pale yellow to orange and much lighter than the heat treated material. Citrine gets its name from the French word for lemon. It is a variety of quartz and adds a splash of warmth to jewelry designs. Citrine is said to signify hope and strength. Citrine is the accepted gem for the 13^th and 17^th wedding anniversaries.

December - Blue Topaz
Blue Topaz is one of three gemstones accepted as the December birthstone. Found in a variety of colors including brown, red, orange, pink, sherry, yellow and colorless, green and blue topaz are naturally very pale and they are often irradiated to produce more intense colors. Sky Blue, Swiss Blue and London Blue are names used in the gem trades to refer to the depth of color. Sky Blue is the lightest blue while London Blue is the darkest. Blue topaz is designated as the gem to give for the 4^th, 19^th, and 23^rd wedding anniversaries.

This List is from the Official Birthstone List of the American National Association of Jewelers, Jewelers of America.  These gemstones were officially adopted in 1912. In the US, this is the accepted list.  Tanzanite was added as an additional birthstone for December by the American Gem Trade Association in October of 2002.