If you were born in December, you are lucky to have a choice of three gems on the modern birthstone list: blue topaz, turquoise and tanzanite. Blue is the color for December, and the traditional birthstone list also includes zircon and lapis lazuli.
Here is some useful information about the December birthstones:
Turquoise has been known and valued for thousands of years. The early mines in Sinai, Egypt, were already worked out in 2000 B.C. Today the finest turquoise are found in Iran. Turquoise was first sent to Europe through Turkey, hence its name, which means "Turkish" in French. The brilliant sky-blue color of turquoise has never lost its fascination to gem-lovers. But due to its relative softness (5-6 on the Mohs scale) and its porous character it requires some care.
Topaz of any type is an important jewelry stone due to its hardness (8 on the Mohs scale) and high refractive index. Topaz comes in many colors, including clear, brown, yellow, orange, red, pink and blue. The blue topaz, with a pale to medium blue color created by irradiation can be found in a wide range of sizes at affordable prices. You'll find a range of shades in blue topaz, ranging from the pale Sky Blue to the deeper Swiss Blue and London Blue.
Tanzanite has become such an important gemstone that in 2002 it was added as an official December birthstone by the American Gem Trade Association. Though tanzanite is extremely popular, it was first discovered only in 1967. The original location in Tanzania is still the only source for tanzanite.
Due to its high refractive index and strong dispersion, zircon has great brilliance and intensive fire. The luster is vitreous to a brilliant sheen. Colored stones get a brilliant or step (emerald) cut. Round stones are often given a "zircon" cut which is similar to a standard round brilliant cut with an extra row of facets at the edges.
Although relatively hard, (rating 6.5-7.5 on the Mohs scale), zircon is somewhat brittle and therefore sensitive to knocks and pressure. The gem has the tendency to wear along facet edges. Its use in rings should therefore be limited to protective settings or occasional wear jewelry.
Natural zircon is brown to orange or red. The coveted blue zircon is achieved by heat treatment. But only some zircon have the right physical structure to turn blue when heated. This is why most blue zircon comes from Cambodia.
Lapis lazuli has been used for thousands of years for jewelry and ornamental objects. Its name is from "lapis," the Latin word for stone, and "azul," the Arabic word for blue. The finest lapis comes from the Badakhshan province of northern Afghanistan, where it has been mined continuously for over 6,000 years.
The unique deep blue color of lapis has never lost its attraction. An affordable stone for its carat weight, it is popular as a cabochon for rings and bracelets and an all-time classic stone with a silver setting. Lapis lazuli is fairly soft, (5-6 on the Mohs scale) and sensitive to strong pressure, high temperatures and household chemicals.