Inclusions are one of the main ways in which gemmologists differentiate between a natural versus a synthetic gemstone. Especially when the stakes are high, in diamonds and sapphires, identifying the correct inclusion is vital. This task is much harder in loupe clean and eye clean stones, like a majority of the gemstones in our collection(which contain the principles of the 4C’s). But on the odd gemstone, we discover inclusions that we can utilise to our advantage in showing that the stone itself is natural. And then there are inclusions which can hardly be seen even under the loupe, but using a microscope they are a whole other world.
What are Rutile Needles?
The term is pretty self-explanatory: needle-like inclusions primarily consisting of mineral rutile. The feature is a common occurrence in natural sapphires. If you observe the image above at the top of the photograph small scratch-like markings can be seen. Those are rutile needle inclusions.
Quite commonly it is easy to mistake these as scratches made when polishing the stone. Why are they different? Upon closer inspection, we see that the needles actually go in two directions, almost 60 degrees from each other. This is a characteristic that is derived from the crystal system of sapphire and the directions in which the crystal growth occurs. The other way to tell apart a scratch from a rutile needle inclusion is that the inclusion is inside the stone while a scratch is on the surface. A scratch also usually doesn’t continue through the facets of the gemstone and will only be present on one facet.
The inclusions can also be confused with the synthetic alternative: curved striations. The rutile needles in the photo are straight lines. Whereas curved striations are much more curved.
In addition, this gemstone has a multitude of inclusions that are present including a healed fracture. This is shown by the faint green circle, as well as along the white line. It also has a fingerprint inclusion as we had discussed in one of the previous journal entries, signalled by a blue line. Plus the white circle surrounds a true alien-like crystal and fluid inclusion. The red arrow points toward an additional crystal included in the background of the stone.
A Different Focus Point
I’ve taken the same zone of the gemstone and changed the focal point to be much deeper than the first image. And lo and behold we see the alien-like inclusion take shape. This I suspect to be a healed fracture inclusion with a portion of fluidity in the inclusion itself. The tail of the inclusion itself has a very thin veil, similar to the inclusion we have already discussed in a previous journal entry. (CLICK HERE for the previous entry.)
From an intrigued perspective It’s unique beauty and structure are quite jaw-dropping. My first recollections were of Toy Story, which I had seen as a child and is very similar to “the claw” in the movie.
A mixture of depth reveals a whole new world. But to tell a natural sapphire the presence of rutile is a hint! Adios Amigos!