Diamond and Its Substitutes
Diamond is the world's hardest gem with the simplest composition. It is a carbon-based natural crystal with a cubic structure. Larger diamonds are rarer. Diamonds frequently contain 0.05%-0.2% impurity elements, the most important of which are N and B. Due to the mixture of trace elements, pure diamonds, which are originally colorless and transparent, display various colors.
Due to their rarity, natural diamonds, especially the larger ones, are extremely expensive. It is challenging to produce larger-sized gem-quality gemstones from synthetic diamonds. Generally speaking, synthetic diamonds are used in cutting and grinding tools. As a result, there are frequently some substitutes to meet the design requirements of jewelry and some products, such as glass, synthetic spinel, synthetic sapphire, zircon, scheelite, strontium titanate, cubic zirconia, etc. The most popular diamond substitute among them is cubic zirconia, which is very similar to diamond in terms of optical and hardness qualities.
Cubic zirconia was first developed by the Soviets, also known as Soviet stone. Cubic single crystals of zirconia are extremely rare in nature and are typically synthesized artificially. Synthetic cubic zirconia is a kind of hard, colorless, and optically flawless crystal. Since 1976, it has been used as a replacement for diamonds due to the fact that it is less expensive, durable, and has an appearance that is very similar to that of diamonds. Synthetic cubic zirconia is known as "fake" diamonds and is often referred to as CZ diamonds. CZ diamonds have been favorably received due to the fact that their price is very low and their appearance is extremely similar to that of natural diamonds. Its primary synthesis technique is still the so-called "cold crucible" method developed by the Soviet Union.
Cubic zirconia differs from natural diamonds in the following aspects:
Hardness
Natural diamond has a high Mohs hardness of 10, which makes it difficult to process. In contrast, cubic zirconia has a Mohs hardness of 8.5 to 9.0, quartz sand has a Mohs hardness of 7, and stainless steel has a Mohs hardness of only 5.5. Gem-grade cubic zirconia can therefore not only fulfill the daily usage requirements, but also facilitate the processing.
Dispersion
Compared to diamond, which has a dispersion of 0.044, cubic zirconia has a dispersion of 0.060. As a result, cubic zirconia appears more brilliant than diamond.
Refractive Index
Cubic zirconia has a refractive index of 2.176, which is slightly lower than that of diamond(2.417). Because of the difference in refractive index, the cutting of cubic zirconia is slightly different from diamonds, which can be observed with close examination under a magnifying glass.
Color
Diamonds that are completely colorless are extremely rare and they typically have a yellowish tinge. However, cubic zirconia can be manufactured into the highest diamond grade, that is, D color. Cubic zirconia is a man-made alternative to diamonds and other precious stones, and it can appear any desired hue to satisfy the needs of customers for colored gemstones by incorporating a number of different trace elements. As an illustration, adding cerium can produce hues of yellow, orange, and red; chromium can produce hues of green; neodymium can produce hues of purple; and so on.
Specific Gravity
Cubic zirconia is 1.7 times heavier than diamond. The difference in specific gravity can be used to differentiate between the two, but this feature is only applicable to distinguish unmounted gemstones.
Heat Transfer Capacity
Cubic zirconia and diamond represent two extremes in terms of thermal conductivity. Because it is such a good thermal insulator, cubic zirconia is typically utilized in the insulation of jet engines; whereas diamond is one of the best heat conductors, with a heat conduction capacity that exceeds that of copper.