‘Bubbles’ in Diamonds?

By Daniel Howell, Ph.D. | 28.01.16
‘Bubbles’ in Diamonds?

Although this article does not discuss fancy color diamonds it is a relevant topic for all diamond industry professionals, as this phenomenon is very common in fancy color, particularly in pink diamonds.

The collective misconception that diamonds hold gas bubbles in their internal structure has forced many manufacturers to develop strange theories and practices as part of their ‘risk management’ strategy. When manufacturers identify an inclusion that appears to be a ‘bubble’, they laser drill a channel to the bubble to release pressure and tension because of concern that the gas will expand due to the high temperature, and crack the stone during the polishing process. This misconception is even adopted by insurance companies who support the procedure in case they need to insure a stone.

One of the biggest misnomers in the diamond industry is the term bubble. It has generated a pervasive misconception that certain features visible within a diamond are trapped gas bubbles. This is NEVER the case. At the great pressures and temperatures that diamonds form under, it is not possible for anything to exist in the form of a gas. Only solids and liquids exist under these extreme conditions. These bubbles are actually inclusions of other minerals that became trapped by the diamond as it grew.

These inclusions represent fragments of the rocks in which the diamonds grew, or they can be the products of the same fluids that the diamonds themselves grew from. The reason for people referring to these inclusions as bubbles is that they look similar in shape and transparency to gas bubbles and can appear empty (picture 1). When the inclusion is as transparent as the diamond surrounding it, it is not obvious that there is anything solid within it. However, there always is.

One reason we know these inclusions are not gases is because they have been extensively studied for decades. Though my work only extends back about 12 years, these studies have been done by some of the most advanced scientific laboratories in the world. This work can be carried out while the inclusions are still trapped within the diamond. Spectroscopic techniques like infrared (IR) and Raman spectroscopy that look at the vibrations of atoms, which are capable of identifying fluids and gases, confirm these transparent inclusions as solid minerals.

Image 2: This diamond also contains two inclusions of colourless olivine. But this time they have had the morphology of the diamond imposed upon them, giving them more defined crystal faces and making them look less like a ‘bubble’. [Image taken by Dr Dan Howell, sample provided courtesy of Dr Jeff Harris, University of Glasgow.]

Image 2: This diamond also contains two inclusions of colourless olivine. But this time they have had the morphology of the diamond imposed upon them, giving them more defined crystal faces and making them look less like a ‘bubble’. [Image taken by Dr Dan Howell, sample provided courtesy of Dr Jeff Harris, University of Glasgow.]

More extensive analysis is also performed when the inclusions are broken out of the diamonds. This can be done by brute force, literally cracking the diamonds just to get to the inclusions, or ...
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