Diamonds come in a variety of natural colors like white, yellow, brown, pink, blue, green, etc. However the most popular diamond color is white. The brilliant shine and sparkle of a white diamond makes it ideal for jewelry. But there is a process to artificially color diamonds to produce fancy colored diamonds in shades like vivid yellow, pink, blue, green and more. These artificially colored diamonds are just as beautiful and valuable as their rare naturally colored counterparts.
Methods of Artificial Coloring
There are two main methods used to artificially color diamonds – HPHT (High Pressure High Temperature) and CVD (Chemical Vapor Deposition). Both alter the chemical composition of a diamond to change its color.
HPHT Method
In the HPHT method, a colorless or pale yellow diamond is placed in a special press device where it is subjected to temperatures of 1800-2500°C and pressures above 5 GPa. This alters the crystal structure of the diamond. Nitrogen impurities present in the diamond get forced into the lattice spaces. The resulting change in structure leads to absorption of certain colors and reflection of others, causing a color change.
HPHT treatment can produce pink, purple, red, orange, yellow and brown diamonds. Blue and green colors are not possible through this method. The most common HPHT colors are pink, blue and yellow.
CVD Method
CVD or chemical vapor deposition is a more complex procedure. Here, a hydrocarbon gas mixture is activated and exposed to a diamond seed under low pressure and high temperature. As the gas mixture breaks down, carbon atoms are slowly deposited on the diamond crystal. At the same time, doping materials like boron or nitrogen are added to alter the diamond’s composition. This gives the finished diamond a modified crystal structure and changed optical properties, resulting in artificial colors.
The CVD process allows a wider range of colors like vivid yellow, pink, purple, orange and blue-green. Blue is the most popular CVD color. CVD also allows better control over the finished diamond’s color strength and distribution. But it takes longer to produce diamonds through CVD.
Characteristics of Artificially Colored Diamonds
Some key traits of HPHT and CVD treated colored diamonds:
- They have the same hardness, brilliance and fire as untreated diamonds, since the core material is still diamond.
- Colors are distributed evenly in CVD diamonds. HPHT colors may show banding.
- They are graded and priced lower than natural fancy color diamonds.
- Treated colored diamonds usually have medium to lower color saturations.
- Common colors are shades of pink, blue and yellow.
- They will show as ‘treated’ or ‘artificial’ on diamond grading reports.
- Clarity enhancement is common to mask imperfections.
- Resale value is lower compared to untreated natural diamonds.
Production Process Steps
Manufacturing artificially colored diamonds involves careful planning and execution. The main steps are:
- Selection: Colorless or pale yellow diamonds are selected as starting material. The candidate diamond should have fewer inclusions and high clarity.
- Cleaning and Analysis: Diamonds are thoroughly cleaned and then analyzed to determine nitrogen content and structure. This data helps plan the treatment.
- HPHT or CVD Treatment: Based on the desired color, diamonds undergo HPHT or CVD processes under strictly controlled conditions to alter their chemical composition.
- Color Grading: The treated diamonds are graded by color saturation, strength and distribution. Re-treatment may be done to modify the color if required.
- Clarity Treatment: Laser or fracture filling treatments are used to improve apparent clarity.
- Cutting and Polishing: Finally, the colored diamonds are precision cut and polished into gems and jewelry stones.
Cost of Artificially Colored Diamonds
Artificially colored diamonds have lower pricing compared to natural fancy color diamonds, due to the following reasons:
- They are produced in labs on a larger scale with greater supply.
- The color treatment process is cheaper than mining natural fancy diamonds.
- Treated diamonds have lower resale value.
- The color produced is not as rare or desirable as natural diamond colors.
However, treated colored diamonds are still an affordable alternative to colorless diamonds of the same carat size. Here is a price comparison of natural vs treated diamonds by color:
| Diamond Type | Color | Price per Carat |
|---|---|---|
| Natural | Pink | $50,000 – $500,000 |
| Treated | Pink | $2,500 – $25,000 |
| Natural | Blue | $50,000 – $1 million |
| Treated | Blue | $3,000 – $50,000 |
| Natural | Yellow | $10,000 – $50,000 |
| Treated | Yellow | $1,000 – $25,000 |
Identification of Treated Diamonds
Treated diamonds may be sold without disclosure by disreputable sellers. But there are ways to identify artificial treatment:
- Check for an authentic diamond grading report by GIA or AGS, which will state any treatments.
- Purchase from reputable and trusted jewelers to ensure full disclosure.
- Examine the diamond closely under a loupe for uneven color banding or concentrations around cavities – signs of treatment.
- Be wary of fancy colors with low clarity or prices that seem too good to be true.
- Get the diamond certified by a qualified independent appraiser if in doubt.
Conclusion
While artificial processes create the same optical effects as natural fancy diamonds, there are differences in value and prestige. Consumers should be informed if the diamond color is artificial or natural. With disclosed treatment, artificially colored diamonds provide an affordable alternative to enjoy these vibrant colors with the brilliance of a real diamond at a fraction of the cost of a mined one. Reputable jewelers openly share all treatment information to help buyers make the right choice.