Check out the inclusions in these natural (heated) sapphires from a bracelet. While the stones match to the unaided eye regarding color, when you get into the stones at high magnification, you see some noticeable differences. There were quite a few interesting inclusions, but I chose to photograph and share these two because they are common sapphire inclusions and easy to see.
On the top, you see what is called a fingerprint. This is a healed fracture within the crystal, either healing in the crystal growth process or in the heating process.
The bottom shows hexagonal growth and color banding. Corundum-- the mineral species of sapphires (and rubies)-- grows in a six-sided shape, and the bands of growth and color follow that pattern. Since a perfectly pure piece of corundum (colorless/white sapphire) doesn't have color, when varying amounts of iron and titanium for blue, vanadium for violet, and iron for green and yellow make their way into the crystal structure as the stone grows it is reflected in the banding. Heating removes the yellow overtones from iron and is the reason most sapphires are heated.
As these are indicators of natural origin, the inclusions themselves help decide value. For me, aside from needing to determine quality for value, I like things like this because, well, they're interesting and I like to share. So, thank you for indulging in my little #microscopemonday moment, and this has been your #gemologicalminute!