- Crystal Shape
Natural diamonds grow octahedrally , which is to say, they have eight equilateral triangle faces. Lab-grown diamonds usually have a cubical growth, meaning they consist of only six equivalent square faces.
- Responsible Disclosure
Terms such as synthetic, man-made, cultured, created etc are used to indicate that a diamond is lab-grown. Conventionally, laser inscription of diamond girdles can also be used as a marker for synthetic diamonds.
- Type IIA Test
Superlative indicator.
Gemological variant diamond that tells how pure is the diamond that makes it up. Type IIA diamonds are colorless since they do not contain elements like Nitrogen. But only less than 2% natural diamonds can be classified as Type IIA.
- Color Zoning
Paramount identifying marker.
HPHT diamonds exhibit Geometric color zoning whereas natural diamonds display color zoning but not in geometric patterns. CVD, on the other hand, are known to show even coloration.
- Inclusions
HPHT diamonds primarily contain metal inclusions like Nickel, Iron, Cobalt since these are used in their production and often get accumulated in the diamond crystals.
CVD diamonds comprises mineral inclusions, owing to the use of Graphite in their manufacturing processes.
- Strain Patterns
When examined between 2 polarized filters:
- Mined Diamonds – Show bright mosaic or Cross-hatched patterns called strain
- CVD – Display a banded strain
- HPHT – Exhibit a weakly banded strain or no strain at all
- Fluorescence
Natural Diamonds
- Present strongest fluorescence under long wave –
- Mostly displaying blue, yellow and white colors.
Synthetic Diamonds
- Most substantial reaction takes place under short wave.
- Mostly showing green, yellow-green, yellow, orange and colors.
- May also display Phosphorescence, which means these diamonds glow for a minute or more even after the lamp is turned off.