Why can't HPHT diamonds be further whiten like the CVD ones?
- Thread starter thecat
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- Jun 11, 2008
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Re: Why can't HPHT diamonds be further whiten like the CVD o
HPHT-grown diamonds come out of the machines with a permanent color. Any color they might have is due to trace amounts of nitrogen (yellow) or boron (blue) that become trapped in the diamond during growth. Treatment cannot remove these trace elements, so a colorless HPHT-grown diamond is the as-grown, unaltered color.
CVD diamonds can come out of the machine as a grayish, brownish or off-white color, depending on the machine and recipe. This color is usually due to atomic-level defects in the carbon-to-carbon atom bonds. These defects can be healed through a high pressure, high temperature treatment process. When the carbon bonds are fixed, they no longer show the brown/gray color, whitening the diamond. CVD diamonds can also have trace amounts of graphite (gray) or nitrogen (yellow) trapped in the diamond, which cannot be removed.
For both growth methods, diamonds with trace amounts of nitrogen (yellow) can be treated with a different process to turn them pink, green or other colors, but these diamonds cannot be further whitened.
HPHT-grown diamonds come out of the machines with a permanent color. Any color they might have is due to trace amounts of nitrogen (yellow) or boron (blue) that become trapped in the diamond during growth. Treatment cannot remove these trace elements, so a colorless HPHT-grown diamond is the as-grown, unaltered color.
CVD diamonds can come out of the machine as a grayish, brownish or off-white color, depending on the machine and recipe. This color is usually due to atomic-level defects in the carbon-to-carbon atom bonds. These defects can be healed through a high pressure, high temperature treatment process. When the carbon bonds are fixed, they no longer show the brown/gray color, whitening the diamond. CVD diamonds can also have trace amounts of graphite (gray) or nitrogen (yellow) trapped in the diamond, which cannot be removed.
For both growth methods, diamonds with trace amounts of nitrogen (yellow) can be treated with a different process to turn them pink, green or other colors, but these diamonds cannot be further whitened.
Re: Why can't HPHT diamonds be further whiten like the CVD o
Thanks for the reply, Eric.
It's very informative. What if a HPHT diamond comes out with brown tint? Can we fix its bonds? Or is it that HPHT won't ever produce brown/grey tinted stones?
Thanks for the reply, Eric.
It's very informative. What if a HPHT diamond comes out with brown tint? Can we fix its bonds? Or is it that HPHT won't ever produce brown/grey tinted stones?
- Joined
- Jun 11, 2008
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- 125
Re: Why can't HPHT diamonds be further whiten like the CVD o
The primary color (white, blue, yellow) in an HPHT growth cycle is determined before starting the cycle. For jewelry-grade diamonds, there is no reason to intentionally grow a brown or gray diamond when the ultimate goal is to be colorless. There are some HPHT recipes that could create brown or gray hues, but would only be used for specific industrial or scientific purposes.
The primary color (white, blue, yellow) in an HPHT growth cycle is determined before starting the cycle. For jewelry-grade diamonds, there is no reason to intentionally grow a brown or gray diamond when the ultimate goal is to be colorless. There are some HPHT recipes that could create brown or gray hues, but would only be used for specific industrial or scientific purposes.
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