In the dazzling world of simulated diamonds, two contenders frequently emerge as popular alternatives: moissanite and cubic zirconia (CZ). Both offer a captivating sparkle at a fraction of the cost of natural diamonds, making them attractive choices for a wide range of jewelry, from fashion pieces to engagement rings. However, beneath their superficial similarities lie fundamental differences in composition, properties, and longevity. Understanding these distinctions is paramount for anyone considering these gemstones, allowing you to make an informed decision based on your priorities for brilliance, durability, and value.
Chemical Composition and Origin:
The most significant difference between moissanite and cubic zirconia lies in their fundamental chemical makeup.
- Moissanite: As discussed in previous articles, moissanite is silicon carbide (SiC). Natural moissanite is incredibly rare, first discovered in a meteorite crater. The moissanite found in jewelry today is almost entirely lab-grown, produced in controlled environments that replicate the conditions necessary to crystallize silicon carbide. This sophisticated manufacturing process ensures consistent quality and purity.
- Cubic Zirconia (CZ): Cubic zirconia is a synthesized crystalline material, specifically zirconium dioxide (ZrO2). It was first discovered in the early 20th century but became widely available as a diamond stimulant in the 1970s. Unlike moissanite, CZ does not exist naturally in its crystalline gem form. It is purely a man-made product, created by heating zirconium dioxide powder to extremely high temperatures and then cooling it slowly to form crystals.
Hardness and Durability (Mohs Scale):
The ability of a gemstone to resist scratching is measured by its hardness on the Mohs scale, which ranges from 1 (softest) to 10 (hardest). This property is crucial for the longevity of a piece of jewelry, especially for items worn frequently.
- Moissanite: Boasts an impressive Mohs hardness of 9.25. This places it as the second hardest gemstone used in jewelry, right after diamond (10). Its high scratch resistance means that moissanite is very durable and well-suited for everyday wear, including engagement rings, as it will resist scratching and maintain its polish for many years.
- Cubic Zirconia: Is significantly softer than moissanite, with a Mohs hardness of 8 to 8.5. While still relatively hard compared to many other materials, it is considerably softer than moissanite and diamond. This lower hardness means that CZ is more susceptible to scratching and abrasion from daily wear. Over time, a CZ stone can accumulate micro-scratches on its surface, which can lead to a dull or cloudy appearance, diminishing its brilliance.
Optical Properties: Brilliance, Fire, and Luster:
The sparkle and beauty of a gemstone are determined by how it interacts with light, specifically its brilliance (white light reflection), fire (dispersion into rainbow colors), and luster (surface reflection).
- Moissanite: Is renowned for its exceptional optical properties. It has a higher refractive index than diamond, meaning it bends light more intensely, resulting in tremendous brilliance. Its dispersion rate is 2.4 times higher than that of a diamond, producing a remarkable “fire” or rainbow effect that is often more pronounced than in diamonds. This vibrant, multi-colored sparkle is a signature characteristic of moissanite. Its luster is adamantine, similar to diamond.
- Cubic Zirconia: Also possesses high brilliance and fire, particularly when newly cut. However, its optical properties differ from moissanite and diamond. CZ has a high refractive index, giving it good brilliance, but its dispersion is generally lower than moissanite’s, resulting in less vibrant fire. More notably, the luster of CZ is vitreous (glassy), which, while still shiny, can appear less brilliant and more artificial compared to the adamantine luster of moissanite and diamond. As CZ accumulates scratches, its surface dulls, further reducing its light performance.
Weight and Density:
Another subtle but discernible difference between the two gemstones is their weight.
- Moissanite: Is slightly lighter than a diamond of the same size, but heavier than cubic zirconia.
- Cubic Zirconia: Is significantly denser and therefore heavier than both moissanite and diamond of the same carat weight. This means a 1-carat CZ will look smaller than a 1-carat diamond or moissanite because its density means it packs more weight into a smaller volume. A jeweler can often distinguish between the two by simply feeling the weight.
Clarity and Color:
Both moissanite and cubic zirconia are typically manufactured to be visually flawless and colorless, especially in their higher grades.
- Moissanite: Lab-grown moissanite is generally produced to be eye-clean, meaning it has no visible inclusions to the naked eye. It can come in various color grades, from truly colorless (D-F range on the GIA scale) to near-colorless (G-I range) and even with slight tints of yellow or green, though the majority of high-quality moissanite sold today is colorless.
- Cubic Zirconia: Is typically manufactured to be entirely colorless and inclusion-free. It can also be produced in a wide array of colors by adding various metal oxides during the synthesis process.
Longevity and Maintenance:
This is where the practical implications of their properties become most apparent.
- Moissanite: Due to its exceptional hardness and resistance to chemical degradation, moissanite maintains its brilliance and integrity for a very long time with proper care. It is highly resistant to scratching, clouding, and discoloration, making it a “forever” stone. Regular cleaning with mild soap and water is usually sufficient to keep it sparkling.
- Cubic Zirconia: While initially brilliant, CZ is less durable and more prone to scratching and dulling over time, especially with daily wear. The surface scratches can trap dirt and oil, making the stone appear cloudy and lifeless. It also tends to absorb oils from the skin and environment more readily than moissanite or diamond, requiring more frequent and thorough cleaning. CZ is generally considered a temporary or fashion jewelry stone, designed for shorter-term wear rather than lifelong heirloom pieces.
Value and Price:
The price difference between moissanite and cubic zirconia is substantial, reflecting their differing production costs, durability, and optical qualities.
- Moissanite: While significantly more affordable than natural diamonds, moissanite is more expensive than cubic zirconia. Its price is determined by its size and quality, but it offers excellent value for a durable, brilliant, and long-lasting gemstone.
- Cubic Zirconia: Is the most inexpensive diamond stimulant available. Its low cost makes it a popular choice for costume jewelry or for those who desire a temporary sparkle without a significant investment.
Thermal Conductivity (for identification):
Another distinguishing factor used in gemology.
- Moissanite: Is an excellent thermal conductor, but its thermal conductivity differs from diamond. Modern diamond testers can differentiate moissanite from diamond.
- Cubic Zirconia: Is a poor thermal conductor, a property that helps gemologists easily distinguish it from both diamond and moissanite using thermal conductivity testers.
Conclusion:
Both moissanite and cubic zirconia serve as popular diamond alternatives, offering a dazzling appearance. However, their differences are profound.
- Cubic Zirconia is an excellent choice for fashion jewelry, occasional wear, or when budget is the absolute primary concern. It offers immediate sparkle at a very low cost, but its beauty is generally short-lived due to its lower hardness and propensity to scratch and dull over time.
- Moissanite stands out as a superior diamond alternative, offering exceptional brilliance, fire, and remarkable durability comparable to diamonds. It is a true “forever” stone that can withstand daily wear and maintain its sparkle for a lifetime, all at a significantly more accessible price point than a natural diamond.
Ultimately, the choice between moissanite and cubic zirconia depends on your specific needs, budget, and expectations for longevity and performance. For a piece intended for daily wear and long-term enjoyment, moissanite is the clear winner, offering a superior balance of beauty, durability, and value.