These inclusions are noticeable and can be seen with a naked eye. This means they drop into a commercial quality. The inclusions are noticeable with a 10x magnification, but not always visible with the naked eye. However, next to fine jewelry, an SI stone will appear cloudier and have a dimmer shine than the better graded stone.
In the SI grade you can find SI-1 and SI-2. SI-1 have less noticeable and fewer inclusions that their SI-2 siblings. The inclusions in both types tend to be medium in size and can be found anywhere on the stone, but they are normally more centered inclusions. The number of inclusions in both types is also variable. There is no rule saying it has to be one inclusion or several. Typically, it is one inclusion setting the grade rather than a variety of small ones.
The most common inclusions in SI-1 gems are crystals (black or white), feathers, knots, needles, cavities or clouds, among others. In SI-2 these same inclusions are more noticeable or visible, either because of their size or quantity.
SI diamonds are a good offer for consumers looking for a quality stone under a certain budget. An SI diamond or colored gemstone can cost significantly less than the same gemstone with a VS grade. This means SI-1 graded stones are in high demand, as it allows buyers to focus on the other three C’s.