If you had to pick one December birthstone, which would it be: zircon, turquoise or tanzanite? From the blue to bluish purple of tanzanite, to the intense blue and green of turquoise, to the rainbow varieties of zircon – there’s a color for everyone (although blue is the most popular color for zircon). If blue is what you’re looking for, all three December birthstones have their own unique take on this favorite hue. Whatever your color, style or budget preference may be, we can help you pick the right December birthstone for you or a loved one.
Zircon commonly occurs as brownish red, which can be popular for its earth tones. However, most gem-quality stones are heat treated until colorless, gold or blue (the most popular color). Blue zircon, in particular, is the alternative birthstone for December.
Color differences in zircon are caused by impurities, some of which (like uranium) can be slightly radioactive. These gemstones are also treated with heat to stabilize the radioactivity.
While radiation can break down zircon’s crystal structure, it plays a crucial role in radiometric dating. Zircon, the oldest mineral on Earth, contains important clues about the formation of our planet.
Colorless zircon, known as Matura Diamond, displays brilliance and flashes of multicolored “fire” that can rival fine diamond. There’s one key difference though: Zircon is more brittle. Though it measures 7.5 on the Mohs scale of hardness, its faceted edges can chip.
Zircon from Australia dates back 4.4 billion years. Australia still leads the world in zircon mining, producing 37 percent of the world’s supply. Other sources include Thailand, Sri Lanka, Tanzania, Cambodia, Canada, and the United States.
Since the Middle Ages, people have believed that zircon gemstones can induce sleep, ward off evil, and promote prosperity.
Admired since ancient times, turquoise is known for its distinct color, which ranges from powdery blue to greenish robin’s egg blue. It’s one of few minerals to lend its name to anything that resembles its striking color.
The word “turquoise” dates back to the 13th century, drawing from the French expression pierre tourques, which referenced the “Turkish stone” brought to Europe from Turkey.
Ancient Persia (now Iran) was the traditional source for sky blue turquoise gemstones. This color is often called “Persian blue” today, regardless of its origin. The Sinai Peninsula in Egypt was also an important historical source of turquoise gems.
The U.S. is now the world’s largest turquoise supplier. Nevada, New Mexico, California, and Colorado have produced turquoise, but Arizona leads in production by value, as well as quality. The stone’s popularity here makes it a staple in Native American jewelry.
Turquoise is found in arid regions where rainwater dissolves copper in the soil, forming colorful nodular deposits when it combines with aluminum and phosphorus. Copper contributes blue hues, while iron and chrome add a hint of green.
Some turquoise contains pieces of host rock, called matrix, which appear as dark webs or patches in the material. This can lower the stone’s value, although the uniform “spiderweb” pattern of Southwestern turquoise is attractive.
Turquoise is sensitive to direct sunlight and solvents like makeup, perfume, and natural oils. The hardest turquoise only measures 6 on the Mohs scale, which made this soft gemstone popular in carved talismans throughout history.
From ancient Egyptians to Persians, Aztecs and Native Americans, kings and warriors alike admired turquoise for thousands of years. It adorned everything from jewelry to ceremonial masks to weapons and bridles—granting power and protection, particularly against falls.
Highly esteemed for its striking namesake color and its ancient history, turquoise's popularity remains timeless.
Despite being found in the late 1960’s, tanzanite did not become one of December’s birthstones until 2002. Tanzanite is the exquisite blue-purple variety of the mineral zoisite that is only found in one part of the world. Named for its limited geographic origin in Tanzania, tanzanite has quickly risen to popularity since its relatively recent discovery.
Zoisite had been around more than a century and a half before this rare blue variety was found in 1967. Trace amounts of vanadium, mixed with extreme heat, cause the blue-purple color—which ranges from pale blue to intense ultramarine with violet undertones.
Due to pleochroism, tanzanite can display different colors when viewed from different angles. Stones must be cut properly to highlight the more attractive blue and violet hues, and deemphasize the undesirable brown tones.
The majority of tanzanite on the market today is heat treated to minimize the brown colors found naturally, and to enhance the blue shades that can rival sapphire.
Tanzanite is still only found on a few square miles of land in Tanzania, near majestic Mount Kilimanjaro. Its price and availability are directly tied to mines in this region, most of which are now slowing production significantly.
Tanzanite measures 6.5 to 7 on the Mohs scale of hardness—which is not nearly as hard as the sapphire it often substitutes. Given its vulnerability to scratch during daily wear and abrasion, tanzanite is better suited for earrings and pendants than rings.
Between its deep blue color and its limited supply, tanzanite is treasured by many, even if your birthday is not in December.