The world of jewelry has, over the last several decades (possibly even a century), seen a drastic revolution as jewelry becomes more available and diverse.
Dazzling pieces were almost always worn by royalty and extremely wealthy members of society because they were very expensive and hard to acquire.
Over time, scientists have come up with innovative methods of creating simulants – stones or gem pieces that bear uncanny resemblances to expensive and hard to attain gemstones such as diamonds.
Cubic zirconia is one such mineral. There have been several natural occurrences of this stone in nature, but the reserves were too small.
It is, however, now produced in controlled lab settings, and it has become one of the most popular semi-precious stones, especially because of its close resemblance to diamonds. So, what is cubic zirconia, what is it made of, and how is it made? Here goes.
What is Cubic Zirconia?
Cubic zirconia is a semi-precious stone used to make all types of jewelry. It is a man-made compound that is made in laboratories in many parts of the world.
One of the characteristics that make it stand out the most is the fact that cubic zirconia resembles diamonds closely and could easily pass for the same.
It is, in fact, almost impossible to tell cubic zirconia and diamonds apart if they are placed side by side. For this reason, cubic zirconia is commonly referred to as the diamond simulant.
Unlike diamonds, cubic zirconia is considered an affordable semi-precious stone. Many manufacturers are working to finesse the look, strength, and durability of the cubic zirconia used in making jewelry.
For this reason, some of it is put through several refining processes like coating it with DLC (diamond-like carbon) which makes it stronger, brighter, and a little more valuable. The process of coating cubic zirconia with DLC is referred to as chemical vapor deposition.
When it comes to physical characteristics, cubic zirconia presents unique features that include a density of between 5.6 and 6.0 g/cm3. It is, in fact, 1.6 times denser than diamond which has a density of 3.5 g/cm3.
Apart from being a dense gemstone, cubic zirconia is also quite hard, and it is placed at 8 to 8.5 on the Mohs scale.
This makes it harder than most other precious and semi-precious stones.
Due to its close resemblance to diamonds, cubic zirconia is used to make jewelry like earrings, neckpieces, watches, bracelets, rings, and many other items.
The mineral is also used in construction and can be used to make windows, lenses, filters, laser elements, and prisms. On occasion, cubic zirconia has been used to make high-grade medical equipment such as scalpels which have a much cleaner and smoother edge than stainless steel blades.
Apart from clear cubic zirconia which resembles diamonds, there are many other color variations for the same. Being that the mineral is made in laboratories, manufacturers can choose to make them in whichever color they prefer.
Colored cubic zirconia is, however, not as popular as clear versions as the main idea is to make jewelry that mimics diamond pieces.
The Raw Materials of Cubic Zirconia
Cubic zirconia is manufactured from a mixture of high purity zirconium oxide powder which is stabilized with calcium and magnesium.
Each of the ingredients used is well regulated during the process to make sure that the cubic zirconium obtained is of high quality.
When manufacturers want to make cubic zirconia that looks like genuine diamonds, they may add a few other ingredients during the manufacturing process.
One of these ingredients is the DLC mentioned above.
The Manufacturing Process of Cubic Zirconia
Manufacturers use three main methods when it comes to the synthetic manufacture and simulation of cubic zirconia.
They are solution growth, melt growth, and extremely high-pressure, high-temperature growth. We are going to look at the solution and melt growth methods.
This is, perhaps, one of the most commonly used methods of manufacturing cubic zirconia.
Solution growth involves many techniques, and each one is used in the manufacture of various stones such as emeralds, rubies, tourmaline, opal, and others.
Different solution growth techniques have been developed over time, and this is mostly because each is suited for specific gemstones.
The most common solution growth techniques are the flux method, hydrothermal method, solid-liquid state reactions, vapor phase deposition, phase transformation, and others.
In essence, solution growth techniques involve growing crystals from an aqueous solution. There are 4 main solution growth techniques which are high-temperature solution growth, low-temperature solution growth, gel growth, and hydrothermal growth.
- Low-temperature solution growth
This technique is divided into three methods; slow cooling method, solvent evaporation method, and temperature gradient method.
The slow cooling method involves pouring a saturated solution with an above-room temperature into a crystallizer which is then thermally sealed. A seed crystal is then introduced, and other crystals form around it at controlled temperatures until they all form one large crystal.
The solvent evaporation method entails establishing an excess of a solute by using the difference between the evaporation rate of the solute and the solvent.
In this method, the solvent loses its particles, causing the volume of the solution to decrease. In many instances, the vapor pressure of the solvent above is greater than that of the solute below, causing the solvent to evaporate much faster.
The solution then becomes super-saturated, causing crystals to begin forming. In this method, manufacturers have to maintain precise temperature, and it can only take a ±0.0005°C temperature variation and a maximum evaporation rate of only a few mm3/h.
The temperature gradient method involves transporting raw materials through a medium whose material is made hot at the source of the item to be grown.
The material is transported to a very cool region where the solution is highly saturated, and this causes crystals to start growing. In this method, a small deviation in temperature between the source and the crystals can affect crystal growth dramatically.
- High-temperature solution growth
Solutions are generally deemed effective at temperatures that are higher than room temperature. In this method, the ingredients of the material (cubic zirconia, in this case) are introduced into a suitable solvent.
When the solution becomes critically saturated, crystals begin to form. The solution has to be at high temperatures for this method to work.
- Hydrothermal growth
This method involves utilizing the growth of both the vapor and solution. In essence, you need an aqueous solution, high temperatures, and high pressure.
The solutions used in this method are usually alkaline in nature while temperatures range between 400 – 600°C. The pressure involved is quite high and has to range from 100 to 1,000 Pa.
To form crystals, you need to have the solution in silver autoclaves which have either gold or silver linings. The concentration gradient necessary to produce crystal growth is largely determined by the difference in temperature between the growth areas and the nutrients.
The temperature difference is usually between 10°C and 100°C.
- Gel growth method
In this method, a very simple principle is applied; a solution of two suitable compounds produces the required crystalline substance.
This process is facilitated by a series of chemical reactions. It requires a gel medium to complete the reaction.
There are two types of gel; physical gel such as gelatin or clay, and chemical gel such as silica and polyacrylamide.
This method entails forming crystals by cooling a molten liquid below its freezing point. In melt growth, no impurities or additives are introduced in the process.
It is the fastest growth method when compared to all others, making it ideal for commercial settings. There are 6 types of melt growth as indicated below.
- Bridgmann Method
Here, polycrystalline material is heated beyond its melting point, then it is gradually cooled from one end where a seed crystal is installed.
This prompts crystals to begin forming along the length of the container. The Bridgmann method can be used in both vertical and horizontal settings.
- Pulling technique (Czochralski technique)
In this method, the charge is melted and is then maintained at a temperature above its melting point. A pulling rod is introduced and is allowed to just touch the melt.
Since the rod is of a lower temperature than the melt, crystals begin to form at its tip. The rod is then gently pulled out of the melt.
There are several factors that influence the rate of pulling, and they include the cooling rate of the rod and the latent heat of fusion of the charge. The seed should be rotated to make sure that the crystal forms uniformly with a cylindrical shape.
- Zone melting method
Here, a small amount of raw material is melted in a large solid charge to make a liquid zone. The crystals then concentrate at the end of a crystal bowl within the system.
- Vernuil method
Here, a fine powder that is chemically pure is introduced to the end of a single oriented crystal seed which is attached to a lowering mechanism.
The powder charge is introduced through a special tapping mechanism. It is important to regulate the oxygen, hydrogen, charge, and descent rate of the seed.
- Kyropoulos technique
In this method, a melt is placed in a crucible, then a single cooled seed is introduced to initiate the crystallization. Heat is gradually reduced to increase the growth of crystals.
- Skull melting process
This method involves high temperatures and is ideal for materials with high melting points.
The cubic zirconia is made in a ‘skull crucible’ which is suited for extremely high temperatures. It can produce cubic zirconium which is at least 10 cm long.
Cutting Cubic Zirconia
After the cubic zirconia crystals are formed, they have to be cut to make them ready for market use. Just like diamonds, cubic zirconia can be cut in many ways, and because it is hard enough, it can be cut in multiple ways to produce high clarity.
Before cutting, a gemstone cutter must carefully examine all the crystals so that they can determine what proportion of the crystal needs to be cut away so as to produce the best clarity.
The cutter must also determine which cut shape will optimize the size of the crystal. In essence, a cutter must use as much of the cubic zirconia as possible to avoid wasting too much of the same.
To allow maximum light penetration, clarity, and dispersion, the cutter must make mathematical calculations to decide which cut is best for the stone, unless it has been specified by a client. This sort of cut is commonly referred to as a brilliant cut. Here is a step-by-step cutting process.
- The gemstone is marked to determine the cleavage planes then it is cleaved to give it its initial shape. Cubic zirconia has the capacity to split in parallel directions from the octahedral face, so it can be cleaved using special tools coated with diamond dust. The stone can also be sawed using tools impregnated with diamond dust. Nowadays, there are programmed machines that cut gemstones to pre-programmed measurements.
- The cut stones are placed in machines that work to round off their sharp edges in a process called rounding up or bruting. The machines are fitted with diamond tools called sharps.
- After the rounding up process, the stone is faceted (given multiple faces) using a cast iron cutting wheel. The stone goes through a second faceting called the secondary facet, then it is polished to make it smooth.
- The faceted and polished stone is then cleaned in boiling acid to remove dirt, oil, and loose diamond powder. The stones are then inspected under a microscope and packaged in a foam casing.
Quality Control of Cubic Zirconia
When checking cubic zirconia for quality, there are 4 major attributes to consider; color, carats, clarity, and cut.
They are referred to as the 4 Cs. In essence, the grade of all 4 attributes is combined to determine the purity, quality, and value of cubic zirconia.
The color of cubic zirconia determines, to a large extent, what its value is going to be. When making diamond simulations, less color translates to more value.
This means that the clearest cubic zirconia stones are more valuable than those that have a haze or tinge of color to them.
When producing colored cubic zirconia, manufacturers look for stones with the best color distribution and saturation, with those that are colored non-uniformly receiving the lowest value.
Colored stones are called fancies, and they are graded based on the rarity, evenness, and tone of color they possess.
This attribute refers to how transparent a stone is. When making cubic zirconia, high-quality melts produce the clearest crystals that are free of impurities.
Variations in materials and additives used can alter the clarity of a stone, and this is why it is important to use high-quality raw materials.
The clearer cubic zirconia is, the more valuable it becomes.
This is possibly the most important attribute of all the 4 Cs. Stones are evaluated using the Brilliant Cut proportions.
The Brilliant Cut was established by a mechanical engineer and diamond cutter called Marcel Tolkowsky in 1919, and it depicts the best way to cut a stone so that it bears maximum brilliancy and fire. This cut was used for diamonds, but it also applies to cubic zirconia as well.
The most brilliant cut entails 58 facets, but in some instances, fewer cuts are allowed. In some shapes, 58 facets cause too much refraction which causes the stone to be less brilliant. Smaller stones can, therefore, be cut with fewer facets.
Over time, however, many other cuts have been introduced, but the main focus remains on how many facets each stone has, as well as the brilliance it bears.
To check for cut flaws, cubic zirconia stones are observed under a microscope. The stones are also checked for refractive index (using a refractometer) and specific gravity.
This refers to the weight of cut cubic zirconia stones. The more they weigh, the more carats they are, and the more valuable they become.
Cubic zirconia is denser than diamonds, meaning that a 1-carat piece is smaller than a 1-carat diamond.
Is cubic zirconia the same as zircon?
No, zircon is not the same as cubic zirconia. Zircon is a naturally occurring substance that is brown in color.
It is made clear through heat treatment and was used as a replacement for diamonds a few decades back.
Is cubic zirconia a real gemstone?
Yes, it is, but it is categorized as a semi-precious stone.
This means that it can be used to make average value jewelry, but cannot be valued the same as diamonds.
Is cubic zirconia worth anything?
Yes, 1 carat of cubic zirconia is valued at $20.
Is cubic zirconia better than diamonds?
Cubic zirconia shares a few characteristics with diamonds, but it also has its own unique features as well.
While diamonds are brilliant, cubic zirconia is fierier and produces rainbow-like colors when observed under natural light.
It is ideal for someone looking for a little dazzle. Diamond is, however, tougher, more beautiful, and more expensive.
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If you are looking to get a piece of jewelry that is beautiful and dazzling but are on a budget, you could try getting one with cubic zirconia inlays.
It is a strong, beautiful, and affordable alternative to many expensive stones, especially diamonds.
Seeing as it is now commercially produced, you will have no trouble finding a good jeweler for your items.
Tiger is a fashion&jewelry lover. He is also a fashion jewelry manufacturer that help thousands of small business to grow and also do business with some big fashion jewelry brands. He is a truly metal expert and he will share some information you are looking for.