Which term describes the type of fracture that extends from the surface inward in a gemstone?

The term that describes a fracture extending from the surface inward in a gemstone is known as a conchoidal fracture. This type of fracture is characterized by smooth, curved surfaces resembling a shell, and it typically occurs in materials that lack cleavage planes. Because conchoidal fractures often manifest in minerals like quartz and glass, they are important for identifying these materials.

In contrast, external fractures refer to those that remain on the surface without penetrating deeply into the stone. Angular fractures involve sharp, jagged edges that are not typically associated with smooth, shell-like surfaces, and pinpoint fractures are very small, often resulting from stress or impact but do not describe a broader fracture pattern like conchoidal fractures do. Recognizing these distinctions is crucial for understanding gemstone properties and their physical behavior.