December's Birthday Gemstones

The month of  December, with all its Holiday shopping, is known for offering a wide range of choices in everything imaginable. The same holds true with the birthstone for the month. Those born in December are offered 5 different choices! Lapis and Zircon are the two most traditional choices, with turquoise being a bit later addition.  The most recent additions to the list are Tanzanite and Blue Topaz. We won’t confuse the issue anymore with the additional stones which are related to the natal sun signs or star signs of those born in December.


This blue rock, properly known as Lapis Lazuli, is actually composed of up to 9 other minerals. It has been mined in northern Afghanistan for thousands of years. Lapis was revered and used by the ancient Egyptians. It was also ground and used in cosmetics and paints. Ultramarine blue paint used ground lapis as a component until synthetic color agents were developed in the 19th century.

Afghanistan still produces some of the world’s finest Lapis, although exports are limited by current conditions in that area. Chile and portions of the former Soviet Union are also major producers of the stone, which may vary from translucent to opaque. An intense, even violetish blue is the preferred color. Some Lapis will show flecks of gold pyrite. Some will show white patches of calcite, which is usually considered to be indicative of the South American variety.

Lapis is relatively soft and should be worn with care, especially in an item such as a ring. It is quite often dyed to improve its color, and may be treated with a wax coating, to improve its appearance and to seal the dye. Sometimes dyeing can be detected with an acetone soaked swab, applied to an inconspicuous area of the stone. Some cleaning methods, such as ultrasonics and steam cleaners, should never be used on Lapis.

Sodalite is the stone most commonly confused with Lapis. Many other stones, such as chalcedony and howlite may be dyed to imitate Lapis, and azurite, azurmalachite, lazulite, and a man-made material from Gilson also mimic the appearance of Lapis.


Zircon, usually in its blue variety, has been traditionally used for December. Most Mother’s jewelry, the pieces featuring children’s birthstones used to use this one, often using a simulated stone with the appearance of genuine zircon. At one time, these stones were plentiful and very inexpensive. Supplies are much more limited now. Virtually all genuine Blue Zircon has been heat treated to improve the color of the stone, and the treatment is undetectable. Some stones do tend to revert to their original color with exposure to light.

Zircon shows a bit of variation in hardness, but all ranges are a bit on the soft side. It abrades easily. It is also risky to clean with an ultrasonic or steam cleaner.

Southeast Asia is the major source for zircon.


This mineral has been used by man for thousands of years. The ancient Egyptians operated mines in the Sinai Peninsula about 5000 years ago. The ancient Kingdom of Persia was also a major source, and the area it comprised is still known for its high quality material. Ancient artifacts using Turquoise have been associated with Pre-Columbian cultures in America and with ancient China and Tibet.

The United States, China, Chile, Mexico, and Australia are major producing countries. Iran and the Sinai Peninsula also still have producing areas. Turquoise is often found in localities associated with copper deposits, and the blue color of turquoise is created by the copper component of the mineral. The presence of iron or chromium creates the greener colors.

Virtually all turquoise on the market is treated in some manner. Dyes may be used to improve colors. Waxes may be used to stabilize the surface, or the material may be impregnated with plastics and resins. A newer stabilizing treatment consists of treating the surfaces with quartz vapor. Reconstituted turquoise is made by molding stone powder with binders and dyes. The material sold as block turquoise is actually a combination of plastic, resin, and dyes, which contains no turquoise.

Many of the “newer” turquoise products are not actually turquoise. Magnesite, dolomite, calcite, howlite, and limestone have all been treated and sold as turquoise, using names such as lime turquoise, yellow turquoise, and white turquoise. Magnesite is also sometimes misrepresented as chalk turquoise.

Turquoise may also be backed with another material, to help prevent cracking. Epoxies and resins are most often used for this process.

Turquoise jewelry should never be cleaned with ultrasonic or steam cleaners. Skin oils and cosmetics may cause turquoise to become greener during normal wear.


While Blue Topaz can occur naturally, most blue topaz on the market today has acquired its color through heat and irradiation treatments. This has made large quantities of previously unsaleable topaz marketable. The production of darker colors requires more, or different  treatment, and these stones will sell for more than the lighter colors.

The color ranges of blue topaz may be similar to the colors seen in aquamarine and zircon, and may be imitated in glass.

The irradiation treatments were first reported on, in depth, in 1981. The government does have oversight of irradiated gemstones and has intervened several times with the jewelry industry to insure that all blue topaz sold in the United States is safe. Please be aware that not all foreign treatments may be in compliance with U.S. standards, and we are not currently aware of any domestic irradiation facilities processing topaz.  Some producers have recently developed diffusion treatments, which only create color in a thin area of the surface of the stone, as an alternative to irradiation. This is being combined with protective surface coatings to protect the thin color zone from damage, in some cases.

Since most of the blue topaz on the market is less than 30 years old, you should find very few pieces of it honestly represented as vintage or antique. It is also a recent addition to the list of recognized birthstones for December.


Tanzanite is the blue and purple gem variety of the mineral zoisite. First properly identified in 1967, this gem made its commercial debut at Tiffany & Co.

Most tanzanite is the product of heat treatment, which removes a yellow/green color component from the stone. Some stones react differently to the treatment and some intense greens are produced, although some in the gem world feel that marketing this material as green tanzanite is incorrect. The supply and pricing of Tanzanite has fluctuated widely over the years, but seems to be relatively stable these days. Supplies dwindled when the stone was linked to terrorist funding. When no evidence of this was found, the industry in Tanzania rebounded, where the government is trying to create some industries relating to the treatment, cutting, and marketing of Tanzanite.

The American Gem Trade Association added Tanzanite to their birthstone list in 2002, as the Tanzanite industry was trying to regain its position in the market after the damage caused by the unsubstantiated rumors about the industry.

This gem is relatively soft and should be worn with care. It should never be cleaned with ultrasonic or steam cleaning methods. While some pieces of tanzanite jewelry may now be as old as 40 years, this is not a gemstone you will find in any true antique pieces.

A simulated Tanzanite, marketed as tanzanique, and man made cubic zirconia in Tanzanite color, are the most widely used simulants for this stone.

Those born in December have more choices in the birthstone category than those born in any other month. Blues, greens, and violets are available in a wide range of prices. You will find selections of these stones in the Antique, Collectible, and Artisan categories on our Jewelry Lane.

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