Identifying Inclusions Found in Natural Gems

Phenakite crystals show up in flux grown emerald. They are always in low relief and are usually associated with flux veils, which is a primary clue to their identification.

Hexagonal platelets are another item that requires attention. Both hematite and platinum crystallize this way. Hematite in a gem indicates that it is natural in origin; platinum means it is a synthetic.

Occasionally bubbles will take a regular shape, so you need to compare all the information at hand, rather than relying solely on these inclusions to indicate a natural origin. Fortunately, inclusions usually come in groups.

Of special interest are rutile inclusions. They are long, straight and usually flat. They are usually gold colored but sometimes they are red. These are only found in quartz and tourmaline. When found, you only have to distinguish between these two species. Long thin, black needles are often confused with rutile. These are actually tourmaline needles and are common in quartz. Sometime rutile will be very thin, which makes them easy to confuse with the hollow growth tubes in beryl and tourmaline.

Cavities in natural gems

Gems frequently have cavities. Their shape can be angular, oval, or irregular. They can have a gas, liquid, or a crystal inside. They are described by their content.

• Single Phase : Single-phase inclusions have no visible contents, although that could be a gas or liquid

• Two Phase : Two-phase inclusions are distinguished by having a bubble of gas suspended in liquid. The gas has a different RI than the liquid, so it stands out clearly. In some cases, the bubble will move when the gem is rotated. This test is helpful when you are unsure of an identification.

• Three Phase : With a three-phase inclusion, there is the addition of a crystal in the cavity. These are much less common, but a treat to find. A three-phase inclusion in an emerald may indicate a Colombian origin, but other sources are also possible.

Fingerprints in natural gems

Gems grow in a violent environment and many break during development. If the conditions for growth are still present, or become present again, the fractures will heal. However, they do not heal without leaving scars. Small cavities, resembling a human fingerprint are a telltale sign of a healed fracture.

Fingerprint inclusions can be mistaken for flux veils. The distinction is that flux is white and opaque; it is coarser and stands out in higher relief. Once you have seen the difference, it is easier to distinguish. If you are just learning, purchase a couple flux grown synthetics for practice. Use different lighting techniques to make the features stand out. It sometimes takes high magnification to make this distinction.

Hydrothermal grown synthetics have liquid and gas filled fingerprints. However, they usually have nail head spicules as well. Flux and hydrothermal grown gems frequently have bits of gold or platinum, which is another distinguishing feature.

A fingerprint is good indication that the gem is of natural origin. Double check to make sure the stone is not hydrothermal or flux grown.

Feathers and Veils in natural gems

Feathers and veils are closely related to fingerprints. They are usually internal fractures, but they can also have fine bits of minerals associated with them. Because they are so difficult to distinguish, they are more important in grading than identification.