Step 5: Advanced Gem Information
To learn more about identifying natural diamonds, read about their inclusions.
Chemical vapor deposition (CVD) diamonds come in sizes up to 3 carats, with a normal range of inclusions.
You can identify CVD diamonds fairly simply. They have a unique strain pattern that doesn’t resemble that of natural diamonds and strong red fluorescence. In addition, they lack the typical “Cape Line” at 415 nm on their absorption spectrum. Instead, they present a strong line at 737 nm.
GE developed the high pressure/high temperature (HPHT) method of growing diamonds. In 2003, a company called Gemesis (now known as Pure Grown Diamonds) improved the process and has created gem-grade diamonds. Producing a colorless stone takes longer than a yellow one, which is worth considerably more. These canary yellow gems tend to have higher clarity grades.
(UPDATE: Be aware that other manufacturers produce colored and colorless diamonds through the HPHT process).
With rough diamonds, one quick clue is the perfect symmetry of the rough crystals. You rarely find perfect form in natural gems, much less a lot of…