Final answer:
An included diamond crystal that reaches the surface of a fashioned diamond is called a knot. Such a feature can affect the gem's surface and disrupt total internal reflection, which is crucial to a diamond's sparkle.
Step-by-step explanation:
An included diamond crystal that extends to the surface of a fashioned diamond is termed a knot. This occurs when the diamond crystal is included within the diamond, making its way to the surface and often affecting the smoothness or the integrity of the diamond's surface. Diamonds are renowned for their hardness and brilliance.
The crystalline structure of a diamond consists of carbon atoms that are covalently bonded to each other, forming a strong three-dimensional tetrahedral network (sp³ hybridization). This network gives diamonds their extreme hardness and high melting points. Moreover, the way light interacts with the carefully crafted angles within a diamond, through processes such as total internal reflection, contributes to their exceptional sparkle and brilliance.
The included diamond crystal, if it extends to the surface, can disrupt the total internal reflection process, leading to potential imperfections on the diamond surface. Knowledge about diamond imperfections like a knot is important for those interested in gemology and the jewelry industry.