Inclusions

Most people see inclusions as flaws. Tiny crystals trapped inside emeralds, silk-like rutile needles threading through sapphires, or carbon spots dotting diamonds are often dismissed as imperfections that diminish value. But this view misses something fundamental about how gemstones form and what makes them genuinely rare.

Inclusions are not accidents—they are geological records, proof of the extraordinary conditions that created each stone. Far from being defects, they often enhance both beauty and worth, turning what appears to be damaged goods into some of the most coveted gems in the world.

Here are some of the more common forms of inclusions:

Colour Zoning

These are areas or bands of alternating color in a gemstone. Colour zoning occurs naturally during the formation of the crystal and is quite common in the rough form. The cutting of the sapphire can greatly diminish or enhance this type of inclusion.

Fingerprint Inclusions

These are networks of tiny liquid-filled tubes that resemble human fingerprints.  Fingerprint inclusions are formed when sapphires re-crystallize to partially heal a fracture zone. These types of inclusions are fairly common in sapphires, but because they are small, they are not likely to negatively impact the quality of the sapphire.

Feathers

These are small inclusions that have the wispy appearance of a feather. These are typically white in colour, and they can impact the structural integrity of the stone if they’re large enough. Feathers are most often microscopic, thin breaks in the sapphire and usually have little impact on the look of the stone.

Cavities

These are voids or holes that extend from the surface of a gemstone into its interior. A common treatment many sapphires will undergo to remedy this type of inclusion is called cavity filling wherein color-infused glass is introduced into the cavity to fill the cracks and fissures.

Silk

These are the fine, rutile needles that create the sleepy transparency of some sapphires. They appear in groups and look like striations in the stone; for this reason they are often referred to as needles. Silk is also responsible for asterism in star sapphires.  

Not all sapphires contain silk. Silk is an example of an inclusion that may actually add value to a sapphire. In moderate amounts, the highly reflective rutile needles scatter light within a cut sapphire, helping to illuminate a stone’s darker facets and enhance its brilliance.