Clarity Enhanced Diamonds
Diamond clarity relates to the appearance of internal inclusions and surface defects of a diamond. Clarity is one of the four C's of diamond grading (clarity, color, cut, carat). Clarity is arguably the most important factor affecting the price and quality of diamonds. However, many consumers consider clarity to be the least important factor when choosing a diamond. Clarity enhancement processes have been around for many years. These clarity enhancement treatments can often increase a flawed diamond's clarity by one or more grades. There are two main ways diamonds can have their clarity artificially improved: fracture filling and laser drilling.
Fracture filling treatments apply the use of resin or glass-like material to fill cracks on a diamond's structure that has a feather or other imperfection. When light attempts to pass through a diamond that contains a feather, the light hits the feather and is redirected. This is why the feather is visible to the naked eye. The silica resin or glass material used to fill the feather has the same optical appearance and refractive index as the diamond itself. This allows light to travel through the treated area, making the crack appear invisible. This fracture filling process is not permanent, however. The resin or glass-like material used to treat the diamond can be worn away over time due to sunlight and high heat or acid from jewelry repair. Many companies who perform clarity enhancement fracture filling offer guarantees for their work. Most of these companies also offer lifetime repairs on the diamond, usually free of charge.
Although the fracture filling process has been around for many years, the first commercial use of fracture filling of natural diamonds was done by Zvi Yehuda. Yehuda, founder of the Yehuda Diamond Company, began commercial marketing his product in 1982. Yehuda keeps the exact process of their treatment secret. The Yehuda process utilizes a combination extremely high temperatures (around 400° C) and high pressure to create their fracture filling process. Many companies now offer this fracture filling process such as Koss and Goldman Oved. These companies are believed to use a similar process to fill their stones.
Laser drilling is a clarity enhancement treatment used to remove minor internal inclusions within a natural diamond. Internal inclusions appear as cloudy areas or dark spots within the diamond. Clouds or dark inclusions are often caused by iron oxide (rust) and other mineral materials such as garnet. These materials become embedded into the diamond while it is forming. The material occupies cavities within the diamond and causes them to appear clouded or black. Lasers are used to drill a small round hole into this cavity. The hole is filled with an acid or other solution which reacts with the foreign material. The remaining substance can be flushed away leaving an empty cavity within the diamond. The cavity can not be seen with the naked eye and magnification is needed to view the hole, which is about the size of a human hair. This cavity is usually left unfilled. However, some diamonds are filled with a foreign substance that reduces the visibility of the drill hole.
Laser drilling does not affect the durability of a diamond and is more permanent than fracture filling. Laser drilling technology has been around for about 30 years.
Detection of Clarity Enhancement
Reputable and honest jewelers always disclose treatment processes of any diamond or gemstone they sell. Consumers should be aware of clarity enhancement processes and how they can be detected. Never hesitate to ask if any diamond has been clarity enhanced. Here are a few ways to tell if clarity enhancement treatment has been used on a diamond.
Fracture filled diamonds may often appear flawless when viewed from the top. However, they exhibit a streak of colored light known as the flash effect. The flash effect appears as a vivid flash of color at the location of the clarity enhancement which disrupts the facet pattern within the stone. It is best to view this color flash while the stone is loose as mounted stones may hide the effect.
Another sign of a fracture filled stone could be the presence of tiny air bubbles within the diamond. These air bubbles are the result of a less effective fracture filling process. Other signs of fracture filled stones include crackled texture, cloudy surface or filled area and loss of filling. These effects can be visible to the naked eye but are better viewed under magnification.
The effects of laser drilling can also be observed but it takes a highly trained eye and usually requires intense magnification. The diamond, when observed face up, would not exhibit any detection as the drilling is usually done perpendicular to the facet. However, with a slight tilt to the diamond, the laser drill hole and tunnel from the laser can be viewed from the surface down to the inclusion. Generally the use of a diamond microscope can help to easily identify an laser drilling.
The Gemological Institute of America will not certify any stone that has undergone fracture filling treatments. However, they will certify diamonds that have undergone laser drilling treatment.