December is unique among the months, boasting not one, but three official birthstones: turquoise, tanzanite, and blue zircon. While blue topaz is also considered an alternative December gemstone, this article will focus on the primary trio, exploring their histories, geological origins, gemological properties, and cultural significance as revealed by available sources. Each of these gemstones offers a distinct shade of blue, reflecting the cool tones of the winter season and offering a diverse range of options for those born in the twelfth month of the year.
History and Lore
Turquoise holds the longest history of human appreciation, with evidence of its use dating back nearly 6,000 years. Ancient Egyptians mined turquoise in the Sinai desert, crafting it into scarab amulets. Persian architects incorporated crushed turquoise into mosque domes, creating a lasting glow that persists today. In the American Southwest, Navajo silversmiths revered turquoise as “stone fallen from the sky,” believing it offered protection from thunder gods. This deep connection to the natural world and spiritual beliefs has endured for millennia.
Zircon, while also ancient in origin, has a less documented early history compared to turquoise. Sources indicate it is often found in proximity to sapphire deposits in locations like Sri Lanka, Australia, Myanmar, Vietnam, and Cambodia.
Tanzanite is the newest of the December birthstones, discovered relatively recently in the Merelani Hills of Tanzania, East Africa. Its introduction to the gem market occurred in the 1960s, quickly gaining popularity for its vibrant blue to violet hues.
Geological Formation and Sources
Turquoise is a semi-translucent to opaque gem, typically ranging in color from blue to green. Its formation occurs in arid regions, often as a secondary mineral in weathered volcanic rocks. Significant sources include Iran, historically known for its prized “robin’s egg blue” turquoise, regardless of its current origin. The term “Persian blue” is now used by trade professionals to describe this intense blue color. In the United States, Arizona and Nevada are currently the primary producers, with notable mines like Kingman and the now-closed Sleeping Beauty mine. China has emerged as the world’s largest producer, with most gem-quality turquoise originating from Hubei Province.
Tanzanite is found in a relatively small area near the Merelani Hills of Tanzania. Its formation is linked to the complex geological processes occurring in this region.
Zircon is sourced from a variety of locations, including Sri Lanka and Australia. It also appears alongside sapphire deposits in Myanmar, Vietnam, and Cambodia.
Gemological Properties
Turquoise’s composition is complex, varying depending on its origin. It is not a crystalline gem in the traditional sense, often containing veins of matrix – remnants of the rock in which it formed.
Tanzanite, a variety of the mineral zoisite, typically begins as brownish in color. Heat treatment is commonly applied to produce the desirable blue to violet hues. This color change is permanent, and does not affect the gem’s durability. Tanzanite registers between 6 and 7 on the Mohs scale of hardness, making it susceptible to scratching and abrasion. It can be cracked by sudden temperature changes or exposure to high heat and is vulnerable to attack by hydrochloric and hydrofluoric acids.
Zircon ranges from 6 to 7.5 on the Mohs scale of hardness. It is often heat-treated to produce blue and colorless varieties, as well as orange, yellow, and red hues. While generally stable when exposed to light, some heat-treated zircons may revert to their original color (typically light brown) after prolonged exposure to bright light. Heat can also alter the color of some zircon specimens.
The following table summarizes the key gemological properties:
| Gemstone | Hardness (Mohs) | Color | Treatment |
|---|---|---|---|
| Turquoise | Not applicable (opaque) | Blue to Green | Often stabilized with resins |
| Tanzanite | 6-7 | Blue to Violet | Heat Treatment |
| Zircon | 6-7.5 | Blue, Colorless, Orange, Yellow, Red | Heat Treatment |
Symbolism and Metaphysical Beliefs
Turquoise has long been associated with calming nerves and promoting well-being. It has been used as a talisman for travelers since ancient times, believed to offer protection on journeys. For those ruled by Jupiter – Pisces and Sagittarius – turquoise is thought to protect energy and provide support when embarking on challenging paths.
While specific metaphysical beliefs regarding tanzanite and zircon are less detailed in the provided sources, the general association of blue gemstones with tranquility, wisdom, and spiritual insight may apply.
Care and Cleaning
Due to its relative softness, tanzanite is best suited for settings in earrings or pendants, minimizing the risk of abrasion. While it can be worn in rings with protective mountings and careful handling, daily wear is not recommended. Cleaning tanzanite should be done with warm, soapy water; ultrasonic and steam cleaners should be avoided.
Zircon, also prone to abrasion, should not be worn during rough activities like gardening or sports. Cleaning can be performed with a soft brush and mild soap in warm water, but ultrasonic and steam cleaners are not recommended.
Turquoise care is not specifically detailed in the provided sources, but given its porous nature, it may benefit from gentle cleaning and avoiding harsh chemicals.
Conclusion
December’s birthstones – turquoise, tanzanite, and zircon – offer a captivating spectrum of blue hues and a rich tapestry of history and lore. From the ancient reverence for turquoise to the modern discovery of tanzanite and the enduring appeal of zircon, these gemstones represent a diverse and compelling selection for those born in the final month of the year. Each stone possesses unique gemological properties and symbolic meanings, providing a personal connection to the beauty and wonder of the natural world.