What Are Treated Diamonds?
Treated diamonds are diamonds that have undergone artificial processes to enhance their quality characteristics, particularly color and clarity. While natural diamonds are formed deep within the Earth’s crust over millions of years without any human intervention, treated diamonds may have been altered after their initial formation.
Understanding Diamond Treatments
Diamonds can be subjected to various treatments to improve their appearance, making flaws more attractive and marketable. These treatments alter a diamond’s natural state, necessitating full disclosure, as they can significantly impact the diamond’s value.
Common Treatments and Their Effects
Most diamond treatments are not permanent and can be reversible. For this reason, internationally accepted diamond grading rules typically prohibit the certification of treated diamonds. One notable exception is laser drilling, a method used to enhance clarity, which is discussed further below.
Certification and Grading
Reputable diamond grading laboratories, such as the DCLA, do not issue grading reports for treated diamonds. Instead, they may provide a letter identifying the diamond as treated, but this letter will not include any quality characteristics. This policy ensures transparency for consumers and helps them make informed decisions regarding their diamond purchases.
When considering a diamond, it is crucial to understand the implications of treatments on its value and quality. By being aware of the differences between natural, synthetic, and treated diamonds, consumers can make more informed choices and select the best option for their needs.
Diamond Clarity Treatments
Laser Drilling
Diamonds often contain dark inclusions, primarily made of graphite, sulfide, or other iron-containing minerals formed during their natural growth process. These visible dark inclusions can diminish the aesthetic appeal of a diamond, making it less desirable than those with lighter or transparent inclusions. To enhance their appearance, diamonds with surface-reaching black inclusions are frequently subjected to a deep boiling process using strong acids. This method dissolves the mineral inclusions without affecting the diamond itself. However, for inclusions that are completely sealed inside the diamond, there are two main methods to access them: traditional laser drilling and internal laser drilling (KM treatment).
1. Traditional Laser Drilling
Traditional laser drilling involves using a high-power laser beam to create a small tunnel from the diamond’s surface to a trapped dark inclusion. The focused, pulsed laser vaporizes a tiny channel, allowing the inclusion to be reached. Once this channel is established, deep boiling in acid or bleach can remove the dark material, making the inclusion less visible. The drill holes appear as fine, straight tunnels leading to the inclusion.
Under internationally accepted diamond certification standards, laser-drilled diamonds can be certified because this treatment is permanent; it does not revert to the original state. However, it must be clearly indicated on the certificate, as laser drilling can improve the diamond’s appearance but may also reduce its overall value.
2. Internal Laser Drilling (KM Treatment)
Internal laser drilling, known as KM treatment (from the Hebrew term “kiduah meyuhad,” meaning “special drill”), differs from traditional laser drilling. Instead of drilling from the surface, a high-powered laser is focused directly on the internal inclusion. The heat causes the inclusion to expand, creating small channels that connect to the surface. After these channels are established, the dark inclusion can be bleached out using strong acid.
KM treatment drill holes can appear irregular, resembling wormholes or step-like channels, and may have disc-like features with irregular boundaries. A careful gemological examination will conclusively identify this treatment. Similar to traditional laser drilling, KM treatment is permanent, allowing these diamonds to be certified, but the treatment must be clearly disclosed on the certificate due to its impact on value.
Fracture Filling
Fracture filling is a clarity enhancement treatment where a glass-like resin is injected into white or bright feather-like fractures that reach the diamond’s surface. While the fractures do not disappear, the resin creates an optical illusion, making them less noticeable to the naked eye.
The process works by allowing light to pass through the filled fractures, reducing their visibility. In some cases, diamonds may first be laser drilled to access a feather that does not reach the surface, and the filling is then injected through this channel.
Trained gemologists can identify fracture-filled diamonds under magnification. A key identifying feature is the “flash effect,” which appears as bright streaks of color due to differences in dispersion between the diamond and the filling material. Other identifying characteristics include gas bubbles, flow structures, and a “crackly” texture in the filling.
It is important to note that fracture filling is not a stable treatment; it is reversible and can be altered by heat. Factors such as jewelry repairs, diamond resetting, cleaning, and even sunlight can degrade the filler or change its color. For this reason, the DCLA does not issue diamond grading certificates for fracture-filled diamonds.
Understanding the various diamond clarity treatments, including laser drilling and fracture filling, is essential for buyers. Being aware of these enhancements can help consumers make informed decisions and assess the true value of a diamond. Always consult a reputable gemological laboratory for accurate certification and disclosure of any treatments.
Diamond Colour Treatments
Coating
Surface coating is a technique that involves applying a thin layer of colored material to the surface of a diamond. This process aims to either mask the underlying body color or enhance a desired hue. Typically, coatings are applied to the pavilion or girdle of the diamond, taking advantage of how light refracts through the stone to create the illusion of uniform color distribution.
The durability of diamond coatings varies significantly based on the materials and methods used for application. Historically, simple paints or inks were employed, which could easily be removed with solvents. Modern techniques use thin optical or chemical films that are more durable but can still wear away due to heat, scratching, abrasion, polishing, or everyday wear.
Trained gemologists can typically identify coated diamonds without much difficulty in a laboratory setting.
Irradiation
Irradiation involves exposing diamonds to high-energy particles in a nuclear reactor. This process embeds these particles within the diamond’s matrix, effectively altering its color. By bombarding diamonds with gamma rays, neutrons, protons, deuterons, or electrons, the internal atomic structure of the diamond is modified, resulting in color centers—electronic defects that change how the diamond absorbs light.
Different irradiation methods produce varying effects, resulting in distinct colors depending on the type of radiation and exposure time. Often, irradiated diamonds undergo a subsequent annealing process to further refine their color.
Due to the complexities involved, identifying irradiated diamonds with standard gemological equipment can be challenging, making advanced testing by a recognized laboratory essential.
Annealing
Annealing is a heat treatment process that involves slowly heating diamonds at moderate temperatures to deepen or alter their color, often following irradiation. This process frequently enhances colored diamonds, resulting in brighter shades of yellow, orange, or pink. The final color achieved through annealing depends on the diamond’s original composition, the temperature applied, and the duration of the treatment.
HPHT Treatment
The High Pressure High Temperature (HPHT) color treatment simulates the extreme conditions under which diamonds naturally form deep within the Earth. By subjecting diamonds to high temperatures and immense pressure, HPHT treatment modifies the diamond’s internal atomic structure, thereby changing how it absorbs light and altering its color.
While HPHT-treated diamonds may occasionally show visual indicators under magnification, these signs are often insufficient for definitive identification. Advanced testing with specialized equipment is necessary to accurately identify HPHT-treated diamonds.
Understanding the various diamond color treatments—coating, irradiation, annealing, and HPHT treatment—is crucial for buyers. Knowledge of these processes can help consumers make informed decisions about the true value and appearance of a diamond. Always consult a reputable gemological laboratory for precise certification and disclosure regarding any treatments applied to a diamond.