Zircon jewellery offers a beautiful and often overlooked option for those seeking a natural gemstone with exceptional brilliance. This mineral has a long and fascinating history, having been used in adornment for centuries across various cultures. As one of the oldest minerals found on Earth, zircon carries a geological significance that few other gemstones can match. Its unique properties and wide color palette make it a distinctive choice for necklaces, rings, and earrings.
What is Natural Zircon?
Natural zircon is a mineral composed of zirconium silicate, represented by the chemical formula $\text{ZrSiO}_4$. It forms in igneous and metamorphic rocks and is widely distributed across the Earth’s crust. Geologists consider zircon to be the oldest mineral on the planet, with specimens found in Australia dating back over 4.4 billion years. This remarkable durability allows the crystal structure to survive intense geological processes.
The stone has been valued as a gemstone throughout history, with its use documented as far back as the Middle Ages. During the Victorian era, blue zircon was a popular choice for English estate jewellery. Its natural occurrence establishes it as a genuine product of nature, distinct from any laboratory-created material. The mineral’s structure is tetragonal, which contributes to its unique optical characteristics.
Zircon Versus Cubic Zirconia
The similar-sounding names of zircon and cubic zirconia (CZ) are the primary source of confusion for many jewellery buyers. Zircon is a naturally occurring mineral, while CZ is a synthetic material created in a laboratory. Chemically, the two are entirely different substances, despite both containing the element zirconium. Natural zircon is zirconium silicate ($\text{ZrSiO}_4$), a compound formed deep within the Earth.
Cubic zirconia is zirconium dioxide ($\text{ZrO}_2$), a material synthesized for commercial use beginning in the 1970s. CZ was developed as an inexpensive simulant to mimic the appearance of a diamond. The difference in origin and chemical composition means that zircon holds a higher value as a natural gem than its synthetic counterpart.
Colors and Optical Properties
Zircon is highly valued for its exceptional optical properties, particularly its high refractive index and dispersion. The refractive index measures how light bends as it passes through the stone, giving the gem remarkable brilliance. Dispersion, often called “fire,” is the ability of a gem to split white light into a spectrum of colors, and zircon exhibits a high degree of this effect. This combination of brilliance and fire allows colorless zircon to closely resemble a diamond.
The natural color range of zircon includes yellow, red, brown, and green hues. The most sought-after color, a vibrant blue, is typically achieved by heat-treating brownish-red zircon material. This heat treatment, often performed at temperatures around 900 to 1000 degrees Celsius, alters the stone’s color to a stable blue or colorless variety. Zircon has a hardness that ranges from 6.5 to 7.5 on the Mohs scale.
Caring for Zircon Jewellery
Zircon jewellery requires careful handling due to the stone’s moderate hardness and a tendency toward brittleness, especially along facet edges. Because it can be scratched by harder gems like diamonds or sapphires, it is advisable to store zircon pieces separately in a soft pouch or a fabric-lined box to prevent abrasion.
The stone is also sensitive to heat, which can cause color changes, particularly in the popular blue varieties. For this reason, avoid exposing zircon to sudden or extreme temperature shifts. Cleaning should be done using mild dish soap mixed with lukewarm water and a very soft-bristled brush. Ultrasonic cleaners and steam cleaners are not recommended, as the intense vibrations or high heat can potentially damage the stone or loosen its setting.