January - Garnet
Garnet is not a single mineral, but describes a group of several closely related minerals. Garnets come in a variety of colors and have many different varieties. However, the most widely-known color of Garnet gemstones is dark red.
February - Amethyst
Amethyst is one of the most popular gemstones, and has been considered valuable since ancient times. Its name derives from the Greek "amethystos", which means "not drunken", as Amethyst in antiquity was thought to ward off drunkenness. Amethyst colors range from light to dark purple, and the transparent deep purple colors are the most highly regarded.
March - Aquamarine
Aquamarine (from Latin: aqua marina, "water of the sea") is a blue or cyan variety of beryl. Aquamarine ranges in color from a faint light blue to blue and bluish-green, with lighter colored stones being the more common type.
April - Diamond
Diamond, the most famed and fabled of all gemstones, is very unique in many ways. Renowned for being the hardest substance on earth, its sparkling fire, durability, and rarity make Diamond the most prized of all gems. No gemstone contains as much allure and interest as does Diamond.
May - Emerald
Emerald, the green variety of Beryl, is the most famous and valuable green gemstone. Its beautiful green color, combined with durability and rarity, make it one of the most expensive gemstones. Deep green is the most desired color in Emeralds. In general the paler the color of an Emerald, the lesser its value.
June - Pearl
Pearls have been highly valued as gemstones since antiquity, and their allure and beauty has always been magnified by the difficulty of obtaining them in early times. Unlike most other gemstones which are minerals, Pearls are organic and are formed by living organisms. They are generally formed within the soft tissue layer of mollusks such as oysters and mussels.
July - Ruby
A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. The ruby is considered one of the four precious stones together with the sapphire, the emerald and the diamond.
August - Peridot
Peridot is a well-known and ancient gemstone. It makes a lovely light green to olive-green gemstone. The intensity of color depends on the amount of iron present in a Peridot's chemical structure; the more iron it contains the deeper green it will be. The most desirable color of Peridot is deep olive-green with a slight yellowish tint.
September - Sapphire
Sapphire is the most precious and valuable blue gemstone. It is a very desirable gemstone due to its excellent color, hardness, durability, and luster. In the gem trade, Sapphire without any color prefix refers to the blue variety of the mineral Corundum.
October - Opal
Opal is the most colorful of gems. Its splendid play of color is unsurpassed, and fine examples can even be more valuable than Diamond. The play of color consists of iridescent color flashes that change with the angle at which the stone is viewed.
November - Citrine
Citrine is the yellow to orange variety of Quartz. Natural Citrine is not common; most Citrine on the gem market is produced by heat treating Amethyst and Smoky Quartz. It takes a relatively low temperature to change the color light to golden yellow, and heating to higher temperatures will give the stone a darker yellow to brownish-red color. The name Citrine is derived from the citron fruit, a yellow fruit similar to the lemon.
December - Blue Topaz
Topaz makes an ideal gem. A good hardness and desirable colors, combined with a relative abundance and availability makes it one the most popular gemstones. The most commonly used colors of Topaz in jewelry are the blue types.