Inclusions inside sapphire

Above, sapphire bare stone (left to right): 6.36 carats pink/orange (Papalacha), 1.63 carats pink, 4.76 carats violet, 5.43 carats violet, 3.03 carats blue, 2.12 carats blue, 8.06 carats yellow, 3.46 carats yellow, 2.00 carats orange, and 1.01 carats dark orange.

Sapphire raw stone (left to right): 9.88 carats pink, 17.80 carats purple, 30.07 carats purple, 42.13 carats blue, 10.84 carats yellow and 5.86 carats yellow orange.

Natural sapphires and rubies have different inclusions inside them. These inclusions can not only identify the origin of the gemstone through detection, but also identify some treatment methods of the gemstone, including heat treatment or other treatment methods.

Natural gemstones all have inclusions. Although there is a saying that the naked eye is clean and the lighting is clean, if you look closely under a multiplier mirror, there will be different inclusions inside the gemstone. When evaluating the clarity, experts will consider the size, quantity, location and overall visibility of the contents to evaluate.

There are different inclusions from different origins. The following are sapphire inclusions from Sri Lanka:

Color Zoning

In gemstones, there will be band-shaped or horn-shaped color divisions. During crystal formation, this naturally occurring color gamut is very common in raw stones. The cutting of sapphire can greatly reduce or enhance this inclusion.

Usually color ribbon will affect the gem and its value, such as uneven color ribbon and layering. It will cause the gem to look particularly dark in an area or may be missing color when viewed from a certain angle.

Feathers

These were fine inclusions with an appearance similar to that of a feather that was slender. They were usually white in color, and if they were large enough, it would affect the structural integrity of the stone. Feathers were usually tiny fine cracks in sapphires, and usually had little effect on the appearance of the gemstone.

Fingerprint Inclusions

These were tiny liquid fillings that resembled human fingerprints. Fingerprint inclusions were formed when sapphires were recrystallized to partially repair the fracture zone. These types of inclusions were rather common in sapphires, but since they were small, they were unlikely to negatively affect the quality of sapphires.

Aura inclusions (the same as those in the "Aura")

These are elliptical or circular fissures surrounding solid or liquid inclusions. These fissures are formed by the radioactive decay of tiny zircon crystals or the stress caused by the high temperature required for heat treatment. This aura inclusion, sometimes looks like small flying insects.

Mineral crystals (the same as the "Aura")

These are light, dark, transparent, or opaque minerals inside gemstones. For example, in sapphires, you can often find tiny crystals of hematite, zircon, spinel, calcite, and mica. White crystals are more popular because the color of sapphires will mask them. Conversely, dark crystals will darken the color and make sapphires look opaque. Liquid Inclusions

Secondary healing fissures refer to the process of gemstone formation when they re-heal after cracking. This healing process may involve the presence of some liquid or gaseous substances, which will fill in the fissures and gradually form inclusions. In sapphires, carbon dioxide is one of the most common inclusions, and they usually exist in the fissures in liquid form. This state of inclusions can be observed, so as to observe whether sapphires have undergone superheat treatment. Fluid inclusions in heat-treated sapphires usually present a burst state.

The following figure shows liquid carbon dioxide (yellow area) with bubbles. When the heat of the microscope warms the sample, the bubbles shrink and eventually disappear. The critical temperature for phase transition is 31.2 ° C.

Silk is a sapphire inclusion, which consists of tiny rutile needles. These needles take on the shape of streaks on stone, so they are called needles. The right amount of silk can make sapphires present silk-like transparency, and it is also one of the sources of starlight in starlight sapphires.

However, not all sapphires contained silk, and silk was an example of an inclusion that could increase the value of sapphires. The right amount of highly reflective rutile needles could scatter light within the cut sapphire, helping to illuminate the darker side of the gem and enhance its brightness. Therefore, sapphires with the right amount of silk would often be considered more valuable gems.

Cavities

These are the voids or holes that extend from the surface of the gemstone to its interior. Many sapphires are subjected to a cavity filling treatment to repair such inclusions. This treatment method usually involves injecting colored glass into the cavity to fill in cracks and cracks.